FakeNet-NG - Next Generation Dynamic Network Analysis Tool
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README.md

 ______      _  ________ _   _ ______ _______     _   _  _____ 
|  ____/\   | |/ /  ____| \ | |  ____|__   __|   | \ | |/ ____|
| |__ /  \  | ' /| |__  |  \| | |__     | |______|  \| | |  __ 
|  __/ /\ \ |  < |  __| | . ` |  __|    | |______| . ` | | |_ |
| | / ____ \| . \| |____| |\  | |____   | |      | |\  | |__| |
|_|/_/    \_\_|\_\______|_| \_|______|  |_|      |_| \_|\_____|

       D   O   C   U   M   E   N   T   A   T   I   O   N

FakeNet-NG is a next generation dynamic network analysis tool for malware analysts and penetration testers. It is open source and designed for the latest versions of Windows (and Linux, for certain modes of operation). FakeNet-NG is based on the excellent Fakenet tool developed by Andrew Honig and Michael Sikorski.

The tool allows you to intercept and redirect all or specific network traffic while simulating legitimate network services. Using FakeNet-NG, malware analysts can quickly identify malware's functionality and capture network signatures. Penetration testers and bug hunters will find FakeNet-NG's configurable interception engine and modular framework highly useful when testing application's specific functionality and prototyping PoCs.

Installation

You can install FakeNet-NG in a few different ways.

Stand-alone executable

It is easiest to simply download the compiled version which can be obtained from the releases page:

https://github.com/fireeye/flare-fakenet-ng/releases

Execute FakeNet-NG by running 'fakenet.exe'.

This is the preferred method for using FakeNet-NG on Windows as it does not require you to install any additional modules, which is ideal for a malware analysis machine.

Installing module

Alternatively you can install FakeNet-NG as a python module using pip:

pip install https://github.com/fireeye/flare-fakenet-ng/zipball/master

Or by obtaining the latest source code and installing it manually:

git clone https://github.com/fireeye/flare-fakenet-ng/

Change directory to the downloaded flare-fakenet-ng and run:

python setup.py install

Installation on Windows requires the following pre-requisite:

Installation on Linux requires the following pre-requisites:

  • Python pip package manager (e.g. python-pip for Ubuntu).
  • Python development files (e.g. python-dev for Ubuntu).
  • OpenSSL development files (e.g. libssl-dev for Ubuntu).
  • libffi development files (e.g. libffi-dev for Ubuntu).
  • libnetfilterqueue development files (e.g. libnetfilter-queue-dev for Ubuntu).

Execute FakeNet-NG by running 'fakenet' in any directory.

No installation

Finally if you would like to avoid installing FakeNet-NG and just want to run it as-is (e.g. for development), then you would need to obtain the source code and install dependencies as follows:

  1. Install 64-bit or 32-bit Python 2.7.x for the 64-bit or 32-bit versions of Windows respectively.

  2. Install Python dependencies:

    pip install pydivert dnslib dpkt pyopenssl pyftpdlib netifaces

    NOTE: pydivert will also download and install WinDivert library and driver in the %PYTHONHOME%\DLLs directory. FakeNet-NG bundles those files so they are not necessary for normal use.

2b) Optionally, you can install the following module used for testing:

pip install requests
  1. Download the FakeNet-NG source code:

    git clone https://github.com/fireeye/flare-fakenet-ng

Execute FakeNet-NG by running it with a Python interpreter in a privileged shell:

python fakenet.py

Usage

The easiest way to run FakeNet-NG is to simply execute the provided executable as an Administrator. You can provide --help command-line parameter to get simple help:

C:\tools\fakenet-ng>fakenet.exe --help
  ______      _  ________ _   _ ______ _______     _   _  _____ 
 |  ____/\   | |/ /  ____| \ | |  ____|__   __|   | \ | |/ ____|
 | |__ /  \  | ' /| |__  |  \| | |__     | |______|  \| | |  __ 
 |  __/ /\ \ |  < |  __| | . ` |  __|    | |______| . ` | | |_ |
 | | / ____ \| . \| |____| |\  | |____   | |      | |\  | |__| |
 |_|/_/    \_\_|\_\______|_| \_|______|  |_|      |_| \_|\_____|

                         Version  1.0
  _____________________________________________________________
                         Developed by            
                      Peter Kacherginsky      
       FLARE (FireEye Labs Advanced Reverse Engineering)       
  _____________________________________________________________ 
Usage: fakenet.py [options]:

Options:
  -h, --help            show this help message and exit
  -c FILE, --config-file=FILE
                        configuration filename
  -v, --verbose         print more verbose messages.
  -l LOG_FILE, --log-file=LOG_FILE

As you can see from the simple help above it is possible to configure the configuration file used to start FakeNet-NG. By default, the tool uses configs\default.ini; however, it can be changed with the -c parameter. There are several example configuration files in the configs directory. Due to the large number of different settings, FakeNet-NG relies on the configuration files to control its functionality.

NOTE: FakeNet-NG will attempt to locate the specified configuration file, first by using the provided absolute or relative path in case you want to store all of your configurations. If the specified configuration file is not found, then it will try to look in its configs directory.

The rest of the command-line options allow you to control the amount of logging output displayed as well as redirecting it to a file as opposed to dumping it on the screen.

Simple run

Before we dive in and run FakeNet-NG let's go over a few basic concepts. The tool consists of several modules working together. One such important module is the Diverter which is responsible for redirecting traffic to a collection of listeners. The Diverter forces applications to interact with FakeNet-NG as opposed to real servers. Listeners are individual services handling incoming connections and allowing us to examine application's traffic (e.g. malware signatures).

Let's launch FakeNet-NG using default settings by running the following command:

C:\tools\fakenet-ng>fakenet.exe

Below is the annotated output log illustrating a sample intercepted DNS request and an HTTP connection:

  ______      _  ________ _   _ ______ _______     _   _  _____
 |  ____/\   | |/ /  ____| \ | |  ____|__   __|   | \ | |/ ____|
 | |__ /  \  | ' /| |__  |  \| | |__     | |______|  \| | |  __
 |  __/ /\ \ |  < |  __| | . ` |  __|    | |______| . ` | | |_ |
 | | / ____ \| . \| |____| |\  | |____   | |      | |\  | |__| |
 |_|/_/    \_\_|\_\______|_| \_|______|  |_|      |_| \_|\_____|

                         Version  1.0
  _____________________________________________________________
                         Developed by
                      Peter Kacherginsky
       FLARE (FireEye Labs Advanced Reverse Engineering)
  _____________________________________________________________

07/06/16 10:20:52 PM [           FakeNet] Loaded configuration file: configs/default.ini
                                                                        /
                                            default configuration file /

07/06/16 10:20:52 PM [          Diverter] Capturing traffic to packets_20160706_222052.pcap
                                                                        /
                                                      PCAP output file /

07/06/16 10:20:52 PM [           FakeNet] Anonymous Forwarder listener on TCP port 8080...
                                    \
                                     \ Anonymous Listener rule

07/06/16 10:20:52 PM [    RawTCPListener] Starting...
07/06/16 10:20:52 PM [    RawUDPListener] Starting...
07/06/16 10:20:52 PM [  FilteredListener] Starting...
07/06/16 10:20:52 PM [        DNS Server] Starting...
07/06/16 10:20:52 PM [    HTTPListener80] Starting...
07/06/16 10:20:52 PM [   HTTPListener443] Starting...
07/06/16 10:20:52 PM [      SMTPListener] Starting...
07/06/16 10:20:52 PM [          Diverter] Starting...
                                       \
                                        \ Listeners starting up

07/06/16 10:20:52 PM [          Diverter] Diverting ports:
07/06/16 10:20:52 PM [          Diverter] TCP: 1337, 80, 443, 25
07/06/16 10:20:52 PM [          Diverter] UDP: 1337, 53
                                          / 
               Summary of diverted ports /

07/06/16 10:21:03 PM [          Diverter] Modifying outbound external UDP request packet:
07/06/16 10:21:03 PM [          Diverter]   from: 192.168.250.140:49383 -> 4.2.2.1:53
07/06/16 10:21:03 PM [          Diverter]   to:   192.168.250.140:49383 -> 192.168.250.140:53
07/06/16 10:21:03 PM [          Diverter]   pid:  456 name: malware.exe
                                                            /
    Intercepted traffic to the DNS server from malware.exe /

07/06/16 10:21:03 PM [        DNS Server] Received A request for domain 'evil.com'.
                                       \
                                        \ Fake DNS Listener handling the above request

07/06/16 10:21:04 PM [          Diverter] Modifying outbound external TCP request packet:
07/06/16 10:21:04 PM [          Diverter]   from: 192.168.250.140:2179 -> 192.0.2.123:80
07/06/16 10:21:04 PM [          Diverter]   to:   192.168.250.140:2179 -> 192.168.250.140:80
07/06/16 10:21:04 PM [          Diverter]   pid:  456 name: malware.exe
                                                            /
    Intercepted traffic to the web server from malware.exe /

07/06/16 10:21:08 PM [    HTTPListener80] Received a GET request.
07/06/16 10:21:08 PM [    HTTPListener80] --------------------------------------------------------------------------------
07/06/16 10:21:08 PM [    HTTPListener80] GET / HTTP/1.0
07/06/16 10:21:08 PM [    HTTPListener80]
07/06/16 10:21:08 PM [    HTTPListener80] --------------------------------------------------------------------------------
                                       \
                                        \ Fake HTTP Listener handling the above request

Notice that each log line has a name of the currently running FakeNet-NG modules. For example, when it is diverting traffic, the logs will be prefixed with the Diverter label:

07/06/16 10:21:03 PM [          Diverter] Modifying outbound external UDP request packet:
07/06/16 10:21:03 PM [          Diverter]   from: 192.168.250.140:49383 -> 4.2.2.1:53
07/06/16 10:21:03 PM [          Diverter]   to:   192.168.250.140:49383 -> 192.168.250.140:53
07/06/16 10:21:03 PM [          Diverter]   pid:  456 name: malware.exe

At the same time, whenever individual listeners are handling diverted traffic, logs will be labeled with the name set in the configuration file:

07/06/16 10:21:03 PM [        DNS Server] Received A request for domain 'evil.com'.

To stop FakeNet-NG and close out the generated PCAP file simply press CTRL-C:

07/06/16 10:21:41 PM [           FakeNet] Stopping...
07/06/16 10:21:42 PM [    HTTPListener80] Stopping...
07/06/16 10:21:42 PM [   HTTPListener443] Stopping...
07/06/16 10:21:42 PM [      SMTPListener] Stopping...
07/06/16 10:21:43 PM [          Diverter] Stopping...

Configuration

In order to take full advantage of FakeNet-NG's capabilities we must understand its configuration file structure and settings. Below is a sample configuration file:

###############################################################################
# Fakenet Configuration

[FakeNet]

DivertTraffic: Yes

###############################################################################
# Diverter Configuration

[Diverter]

NetworkMode:            Auto

LinuxRedirectNonlocal:  *
LinuxFlushIptables:     Yes
LinuxFlushDNSCommand:   service dns-clean restart

DumpPackets:            Yes
DumpPacketsFilePrefix:  packets

ModifyLocalDNS:         No
StopDNSService:         Yes

RedirectAllTraffic:     Yes
DefaultTCPListener:     RawTCPListener
DefaultUDPListener:     RawUDPListener

###############################################################################
# Listener Configuration

[DNS Server]
Enabled:     True
Port:        53
Protocol:    UDP
Listener:    DNSListener
DNSResponse: 192.0.2.123
NXDomains:   0

[RawTCPListener]
Enabled:     True
Port:        1337
Protocol:    TCP
Listener:    RawListener
UseSSL:      No
Timeout:     10

The configuration file is broken up into several sections.

  • [FakeNet] - Controls the behavior of the application itself. The only valid option at this point is DivertTraffic. When enabled, it instructs the tool to launch the appropriate Diverter plugin and intercept traffic. If this option is disabled, FakeNet-NG will still launch listeners, but will rely on another method to direct traffic to them (e.g. manually change DNS server).

  • [Diverter] - Settings for redirecting traffic. Covered in detail below.

  • [Listener Name] - A collection of listener configurations. Each listener has a set of default settings (e.g. port, protocol) as well as listener specific configurations (e.g. DumpHTTPPosts for the HTTPListener).

Diverter Configuration

Supposing you have enabled the DivertTraffic setting in the [FakeNet] configuration block, the tool will enable its traffic redirection engine to which we will call Diverter from now on as a reference to the excellent WinDivert library used to perform the magic behind the scenes on Windows platforms (the Linux implementation of the Diverter uses python-netfilterqueue).

The Diverter will examine all of the outgoing packets and match them against a list of protocols and ports of enabled listeners. If there is a listener listening on the packet's port and protocol, then the destination address will be changed to the local machine's IP address where the listener will handle the request. At the same time, responses coming from the listener will be changed so that the source IP address would appear as if the packet is coming from the originally requested host.

You can optionally enable the DumpPackets setting to store all traffic observed by FakeNet-NG (redirected or forwarded) to a PCAP file. It is possible to decrypt SSL traffic between an intercepted application and one of the listeners with SSL support. Use the instructions at the following page:

https://wiki.wireshark.org/SSL

The keys privkey.pem and server.pem used by FakeNet-NG's servers are in the application's root directory.

  • NetworkMode - Specify the network mode in which to run FakeNet-NG.
    • Valid settings are:
      • SingleHost: manipulate traffic from local processes.
      • MultiHost: manipulate traffic from other systems.
      • Auto: use whatever NetworkMode is most functional on the current platform.
    • Not all platforms currently support all NetworkMode settings. Here is the current status of support:
      • Windows supports only SingleHost
      • Linux supports MultiHost and experimentally supports SingleHost mode (works with the exception of process, port, and host blacklisting and whitelisting).
    • For now, leave this set to Auto to get SingleHost mode on Windows and MultiHost mode on Linux.

The Diverter generally supports the following DNS-related setting:

  • ModifyLocalDNS - point local machine's DNS service to FakeNet-NG's DNS listener.

The Windows implementation of Diverter supports the following DNS-related setting:

  • StopDNSService - stops the Windows DNS client service (Dnscache). This allows FakeNet-NG to see the actual processes resolving domains as opposed to the generic 'svchost.exe' process.

The Linux implementation of Diverter supports the following settings:

  • LinuxRedirectNonlocal - When using FakeNet-NG to simulate Internet connectivity for a different host, this specifies which externally facing network interfaces to re-route to FakeNet-NG.

  • LinuxFlushIptables - Flush all iptables rules before adding rules for FakeNet-NG. The Linux Diverter will restore the old rules as long as its termination sequence is not interrupted.

  • LinuxFlushDnsCommand - Specify the correct command for your Linux distribution to flush the DNS resolver cache if applicable.

  • DebugLevel - Specify fine-grained debug events to display. Refer to fakenet/diverters/linutil.py for valid labels.

Redirecting All Traffic

By default the Diverter will only intercept traffic that has a dedicated listener created for it. However, by enabling RedirectAllTraffic setting and configuring the default TCP and UDP handlers with the DefaultTCPListener and DefaultUDPListener settings it is possible to dynamically handle traffic going to ports not explicitly defined in one of the listeners. For example, let's look at a sample configuration which redirects all traffic to local TCP and UDP listeners on ports 1234:

RedirectAllTraffic: Yes
DefaultTCPListener: TCPListener1234
DefaultUDPListener: UDPListener1234

NOTE: We are jumping a bit ahead with listener definitions, but just consider that TCPListener1234 and UDPListener1234 will be defined in the section below.

With the RedirectAllTraffic setting, FakeNet-NG will modify not only the destination address, but also the destination port so it can be handled by one of the default listeners. Below is a sample log of traffic destined to an external host IP address 1.1.1.1 on port 4444 which was redirected to the default listener on port 1234 instead:

07/06/16 01:13:47 AM [          Diverter] Modifying outbound external TCP request packet:
07/06/16 01:13:47 AM [          Diverter]   from: 192.168.66.129:1650 -> 1.1.1.1:4444
07/06/16 01:13:47 AM [          Diverter]   to:   192.168.66.129:1650 -> 192.168.66.129:1234
07/06/16 01:13:47 AM [          Diverter]   pid:  3716 name: malware.exe

It is important to note that traffic destined to the port from one of the explicitly defined listeners will still be handled by that listener and not the default listener. For example, default UDP listener will not handle DNS traffic if a separate UDP port 53 DNS listener is defined.

One issue when enabling the RedirectAllTraffic options is that you may still want to let some traffic through to ensure normal operation of the machine. Consider a scenario where you are trying to analyze an application that still needs to connect to an external DNS server. You can utilize the BlackListPortsTCP and BlackListPortsUDP settings to define a list of ports to which traffic will be ignored and forwarded unaltered:

BlackListPortsUDP: 53

Some other Diverter settings that you may consider are ProcessBlackList and HostBlackList which allow Diverter to ignore and forward traffic coming from a specific process name or destined for a specific host respectively.

Listener Configurations

Listener configurations define the behavior of individual listeners. Let's look at a sample listener configuration:

[TCPListener1234]
Enabled:     True
Port:        1234
Protocol:    TCP
Listener:    RawListener
UseSSL:      Yes
Timeout:     10

The configuration above consists of the listener name TCPListener1234. It will be used for logging purposes so you can distinguish between different listeners handling connections even if they are handling the same protocol.

The following settings are generic for all listeners:

  • Enabled - specify whether or not the listener is enabled.
  • Port - TCP or UDP port to listen on.
  • Protocol - TCP or UDP
  • Listener - Listener name to handle traffic.
  • ProcessWhiteList - Only traffic from these processes will be modified and the rest will simply be forwarded.
  • ProcessBlackList - Traffic from all but these processes will be simply forwarded and the rest will be modified as needed.
  • HostWhiteList - Only traffic to these hosts will be modified and the rest will be simply forwarded.
  • HostBlackList - Traffic to these hosts will be simply forwarded and the rest will be modified as needed.
  • ExecuteCmd - Execute command on the first connection packet. This feature is useful for extending FakeNet-NG's functionality (e.g. launch a debugger on the connecting pid to help with unpacking and decoding.)

The Port and Protocol settings are necessary for the listeners to know to which ports to bind and, if they support multiple protocol (e.g RawListener), decide which protocol to use. They are also used by the Diverter to figure out which ports and protocols to redirect.

The Listener setting defines one of the available listener plugins to handle redirected traffic. The current version of FakeNet-NG comes with the following listeners:

  • DNSListener - supports DNS protocol and replies to A records with either a local machine's IP address or a configurable address in the DNSResponse setting. You can also set the NXDomains attribute to the number of requests the listener should ignore. This way you may be able to get the malware to request all of its backup C2 controller names. The listener supports both TCP and UDP protocols.
  • RawListener - supports basic TCP and UDP binary protocols. The default behavior is to simply echo the received packets back to the client. Supports SSL connections.
  • HTTPListener - supports HTTP and HTTPS protocols. Responds with different files in the configurable Webroot directory based on the requested file extension. Optionally dumps POST requests to a configurable file which can be specified using DumpHTTPPosts and DumpHTTPPostsFilePrefix settings.
  • SMTPListener - supports SMTP protocol.

NOTE: FakeNet-NG will attempt to locate the webroot directory, first by using the provided absolute or relative paths. If the specified webroot path is not found, then it will try to look in its defaultFiles directory.

As a special case, the Windows Diverter implementation automatically responds to all ICMP requests while running. So in case a malware attempts to ping a host to test connectivity it will get a valid response. The Linux Diverter logs and forwards all ICMP packets to localhost.

Listener Filtering

FakeNet-NG supports several filtering rules consisting of process and host blacklists and whitelists. The whitelists are treated as the rules that allow connections to the listeners while the blacklists are used to ignore the incoming connections and let them to be simply forwarded.

For example, consider the configuration below with process and host filters:

[FilteredListener]
Enabled:     True
Port:        31337
Protocol:    TCP
Listener:    RawListener
UseSSL:      No
Timeout:     10
ProcessWhiteList: malware.exe, ncat.exe
HostBlackList: 5.5.5.5

The FilteredListener above will only handle connection coming from the processes malware.exe and ncat.exe, but will ignore any connections destined for the host 5.5.5.5. Meaning that if a process called test.exe attempted to connect on port 31337 it will not be redirected to the listener and will be forwarded to wherever it was originally intended if the route is available.

At the same time of the process malware.exe attempted to connect to port 31337 on any host other than 5.5.5.5 it will be diverted to the FilteredListener. Any connections from the process malware.exe destined to 5.5.5.5 would be allowed through.

Listener Command Execution

Another powerful configuration setting is ExecuteCmd. It essentially allows you to execute an arbitrary command on the first detected packet of the connection. The value of ExecuteCmd can use several format string variables:

  • {pid} - process id
  • {procname} - process executable name
  • {src_addr} - source address
  • {src_port} - source port
  • {dst_addr} - destination address
  • {dst_port} - destination port

Consider a scenario of a packed malware sample which connects to a configured C2 server on port 8443 (Use RedirectAllTraffic if the port is not known). In many cases the malware would unpack itself by the time it makes the connection making that point in execution ideal to attach to the process with a debugger and dump an unpacked version of it for further analysis.

Let's see how this can be used to automatically launch a debugger on the first connection:

[C2Listener]
Enabled:     True
Port:        8443
Protocol:    TCP
Listener:    RawListener
UseSSL:      Yes
Timeout:     300
ProcessWhiteList: malware.exe
ExecuteCmd:  C:\Program Files (x86)\Windows Kits\10\Debuggers\x86\windbg.exe -p {pid}

Once FakeNet-NG detects a new connection coming from the whitelisted process malware.exe (this setting is optional), it will automatically launch windbg and attach it to the connecting process.

NOTE: You might want to extend the normal Timeout setting in case the malware needs to further interact with the listener.

Anonymous Listener

There is a special use case where you can create a new listener configuration without defining the actual listener to handle it:

[Forwarder]
Enabled:     True
Port:        8080
Protocol:    TCP
ProcessWhiteList: chrome.exe

Without a listener defined, FakeNet-NG will still divert traffic to the local machine, but a separate listener must be launched by the user. For example, you could have an HTTP proxy listening for connections on port 8080 and let FakeNet-NG intercept all the traffic from applications which do not use system's proxy server settings or use hard-coded IP addresses. Using anonymous listeners you can bring FakeNet-NG's advanced traffic and process filtering capabilities to 3rd party tools.

You may also want to enable Diverter's ProcessBlackList setting to allow the external tool to communicate out to the Internet. For example, to allow an HTTP proxy to forward proxied traffic add its process name to the process blacklist. For example, add the following process to let Burp Proxy to communicate out to the Internet:

ProcessBlackList: java.exe

In the scenario where application communicates on an unknown port, but you still want to redirect it to the anonymous listener on port 8080 you can define the default listener as follows:

RedirectAllTraffic: Yes
DefaultTCPListener: ForwarderTCP
DefaultUDPListener: RawUDPListener

Finally, to allow DNS traffic to still go to the default DNS server on the Internet, while redirecting all other traffic, add port 53 to the Diverter's UDP port blacklist as follows:

BlackListPortsUDP: 53

Development

FakeNet-NG is developed in Python which allows you to rapidly develop new plugins and extend existing functionality.

Developing Listeners

All listeners must implement just two methods: start() and stop(). Below is a sample listener template:

import logging

import sys

import threading
import socket

class MyListener():

    def __init__(self, config, name = 'MyListener', logging_level = logging.INFO):
        self.logger = logging.getLogger(name)
        self.logger.setLevel(logging_level)
            
        self.config = config
        self.name = name

        self.logger.info('Starting...')

        self.logger.debug('Initialized with config:')
        for key, value in config.iteritems():
            self.logger.debug('  %10s: %s', key, value)

    def start(self):

        # Start listener
        # ...

    def stop(self):

        # Stop listener
        # ...

The main listener class MyListener() will be provided with a parsed configuration dictionary containing information such as port to listen on, protocol, etc. The main listener class will also receive the current listener instance name and the logging info set by the user.

The only requirement for listener implementation is that you use threading so that when FakeNet-NG calls the start() method, the listener will not block but spawn a new thread that handles incoming connections.

Another requirement is to ensure that the listener can reliably shutdown when the stop() method is called. For example, make use of connection timeouts to ensure that the listener does not block on some connection for too long.

The logging convention used by FakeNet-NG's listeners is to use the self.logger object for the output. That way the logging is uniform across the application. For example to display an error or warning you would use the following:

self.logger.error("This is an error")
self.logger.warning("This is a warning")

Finally, after you finish developing the listener, copy it to the listeners\ directory and append you module name to __all__ varialbe in the listeners\__init__:

__all__ = ['RawListener', 'HTTPListener', 'DNSListener', 'SMTPListener', 'MyListener']

At this point you can let the application use the newly created listener by adding it to the configuration file:

[MyAwesomeListener]
Enabled:     True
Port:        1337
Protocol:    TCP
Listener:    MyListener

Developing Diverters

FakeNet-NG uses the open source WinDivert library in order to perform the traffic redirection on Windows Vista+ operating systems. The implementation of the Windows Diverter is located in fakenet\diverters\windows.py.

FakeNet-NG uses the open source python-netfilterqueue Cython module to perform traffic redirection on Linux. The Linux Diverter implementation is located in fakenet\diverters\linux.py.

Much Windows-specific functionality is implemented in fakenet\diverters\winutil.py using ctypes to call many of the Windows API functions directly. Likewise, much Linux-specific functionality is implemented in fakenet\diverters\linutil.py.

For detailed information on Diverter internals specific to Linux, see docs/internals.md.

It is planned to continue expanding the support for traffic diversion.

Building standalone executables

If you would like to generate a stand-alone executable you would need to install the PyInstaller module:

pip install pyinstaller

To generate the exe file run the pyinstaller as follows:

pyinstaller fakenet-ng.spec

The standalone executable will be available in the dist/ directory.

This has not been tested for Linux.

Known Issues

Does not work on VMWare with host-only mode enabled

See "Not Intercepting Traffic" below.

Not Intercepting Traffic

In order to for FakeNet-NG to intercept and modify the packet, there must exist a valid network route for the packet to reach its destination.

There is an easy way to check whether or not you have routes set up correctly. Without the tool running attempt to ping the destination host. You should observe either a valid response or a timeout message. If you receive a destination not reachable error instead, then you do not have a valid route.

This is usually caused by your gateway being either not set or not reachable. For example, on a VMWare machine with host-only mode your machine will not have the gateway configured thus preventing FakeNet-NG from seeing any traffic.

To correct this issue, manually configure your primary interface to the gateway in the same subnet. First check the interface name:

C:\>netsh interface show interface

Admin State    State          Type             Interface Name
-------------------------------------------------------------------------
Enabled        Connected      Dedicated        Local Area Connection

In this case the interface name is "Local Area Connection" so we will use it for the rest of the commands.

Manually configure the interface IP address and gateway as follows:

C:\>netsh interface ip set address name="Local Area Connection" static 192.168.249.123 255.255.255.0 192.168.249.254

Manually set the DNS server IP address

C:\>netsh interface ip set dns name="Local Area Connection" static 4.2.2.2

If you are still having issue ensure that the gateway IP address itself is routable.

DNS Not Resolving Names

Ensure that the DNS Listener successfully bound to its port. Errors such as the following indicate that the DNS Listener did not successfully bind:

05/01/17 11:11:16 AM [           FakeNet] Error starting DNSListener listener:
05/01/17 11:11:16 AM [           FakeNet]  [Errno 98] Address already in use

Use netstat, tcpview, or other tools to discover what application is bound to the port, and refer to the corresponding operating system or application documentation to disable the service.

For example, Ubuntu commonly enables the dnsmasq service in /etc/NetworkManager/NetworkManager.conf with the line dns=dnsmasq. Disabling this (such as by commenting it out) and restarting the network-manager service (e.g. service network-manager restart) is sufficient to free the port before re-launching FakeNet-NG.

In newer versions of Ubuntu or in other distributions, using lsof -i may reveal that systemd-resolved is used instead. In these cases, try:

sudo systemctl stop systemd-resolved
sudo systemctl disable systemd-resolved

Error: Could not locate WinDivert DLL or one of its components

Please ensure that FakeNet-NG is extracted to the local C: drive to make sure the WinDivert driver is loaded correctly.

Error: The application has failed to start because its side-by-side configuration is incorrect.

This error may occur when running a stand-alone executable version of Fakenet. Please download and install Visual C++ 2008 runtime executable.

Limitations

  • Only Windows Vista+ is supported for SingleHost mode. Please use the original Fakenet for Windows XP/2003 operating systems.

  • Only Linux is supported for MultiHost mode.

  • Old versions of python-netfilterqueue can cause a segmentation fault in python. If you experience this issue, check that you are using the latest version of python-netfilterqueue.

  • Due to the hard-coded buffer size used by python-netfilterqueue, the Linux Diverter does not correctly handle packets greater than 4,016 bytes in size. In practice, this does not affect Linux MultiHost mode for interfaces configured with the conventional 1,500 byte maximum transmittal unit (MTU). If the Linux interface you are using with FakeNet-NG supports an MTU greater than 4016, you will need to recompile python-netfilterqueue to support a buffer size of <your_mtu> + 80 (python-netfilterqueue devotes 80 bytes of the buffer to overhead).

  • Local machine only traffic is not intercepted on Windows (e.g. if you tried to connect directly to one of the listeners).

  • Only traffic using TCP, UDP, and ICMP protocols is intercepted.

Credits

  • FakeNet-NG was designed and developed by Peter Kacherginsky.
  • Special thanks to Andrew Honig, Michael Sikorski and others for the original FakeNet which was the inspiration to develop this tool.
  • The Linux Diverter was designed and developed by Michael Bailey.

Contact

For bugs, crashes, or other comments please contact peter.kacherginsky@fireeye.com or michael.bailey@fireeye.com.