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##! This script provides a default set of actions to take for "weird activity"
##! events generated from Zeek's event engine. Weird activity is defined as
##! unusual or exceptional activity that can indicate malformed connections,
##! traffic that doesn't conform to a particular protocol, malfunctioning
##! or misconfigured hardware, or even an attacker attempting to avoid/confuse
##! a sensor. Without context, it's hard to judge whether a particular
##! category of weird activity is interesting, but this script provides
##! a starting point for the user.
@load base/utils/conn-ids
@load base/utils/site
@load ./main
module Weird;
export {
## The weird logging stream identifier.
redef enum Log::ID += { LOG };
redef enum Notice::Type += {
## Generic unusual but notice-worthy weird activity.
Activity,
};
## The record which is used for representing and logging weirds.
type Info: record {
## The time when the weird occurred.
ts: time &log;
## If a connection is associated with this weird, this will be
## the connection's unique ID.
uid: string &log &optional;
## conn_id for the optional connection.
id: conn_id &log &optional;
## A shorthand way of giving the uid and id to a weird.
conn: connection &optional;
## The name of the weird that occurred.
name: string &log;
## Additional information accompanying the weird if any.
addl: string &log &optional;
## Indicate if this weird was also turned into a notice.
notice: bool &log &default=F;
## The peer that originated this weird. This is helpful in
## cluster deployments if a particular cluster node is having
## trouble to help identify which node is having trouble.
peer: string &log &optional &default=peer_description;
## This field is to be provided when a weird is generated for
## the purpose of deduplicating weirds. The identifier string
## should be unique for a single instance of the weird. This field
## is used to define when a weird is conceptually a duplicate of
## a previous weird.
identifier: string &optional;
};
## Types of actions that may be taken when handling weird activity events.
type Action: enum {
## A dummy action indicating the user does not care what
## internal decision is made regarding a given type of weird.
ACTION_UNSPECIFIED,
## No action is to be taken.
ACTION_IGNORE,
## Log the weird event every time it occurs.
ACTION_LOG,
## Log the weird event only once.
ACTION_LOG_ONCE,
## Log the weird event once per connection.
ACTION_LOG_PER_CONN,
## Log the weird event once per originator host.
ACTION_LOG_PER_ORIG,
## Always generate a notice associated with the weird event.
ACTION_NOTICE,
## Generate a notice associated with the weird event only once.
ACTION_NOTICE_ONCE,
## Generate a notice for the weird event once per connection.
ACTION_NOTICE_PER_CONN,
## Generate a notice for the weird event once per originator host.
ACTION_NOTICE_PER_ORIG,
};
## A table specifying default/recommended actions per weird type.
const actions: table[string] of Action = {
["unsolicited_SYN_response"] = ACTION_IGNORE,
["above_hole_data_without_any_acks"] = ACTION_LOG,
["active_connection_reuse"] = ACTION_LOG,
["bad_HTTP_reply"] = ACTION_LOG,
["bad_HTTP_version"] = ACTION_LOG,
["bad_ICMP_checksum"] = ACTION_LOG_PER_ORIG,
["bad_ident_port"] = ACTION_LOG,
["bad_ident_reply"] = ACTION_LOG,
["bad_ident_request"] = ACTION_LOG,
["bad_rlogin_prolog"] = ACTION_LOG,
["bad_rsh_prolog"] = ACTION_LOG,
["rsh_text_after_rejected"] = ACTION_LOG,
["bad_RPC"] = ACTION_LOG_PER_ORIG,
["bad_RPC_program"] = ACTION_LOG,
["bad_SYN_ack"] = ACTION_LOG,
["bad_TCP_checksum"] = ACTION_LOG_PER_ORIG,
["bad_UDP_checksum"] = ACTION_LOG_PER_ORIG,
["baroque_SYN"] = ACTION_LOG,
["base64_illegal_encoding"] = ACTION_LOG,
["connection_originator_SYN_ack"] = ACTION_LOG_PER_ORIG,
["contentline_size_exceeded"] = ACTION_LOG,
["crud_trailing_HTTP_request"] = ACTION_LOG,
["data_after_reset"] = ACTION_LOG,
["data_before_established"] = ACTION_LOG,
["DNS_AAAA_neg_length"] = ACTION_LOG,
["DNS_Conn_count_too_large"] = ACTION_LOG,
["DNS_NAME_too_long"] = ACTION_LOG,
["DNS_RR_bad_length"] = ACTION_LOG,
["DNS_RR_length_mismatch"] = ACTION_LOG,
["DNS_RR_unknown_type"] = ACTION_LOG,
["DNS_label_forward_compress_offset"] = ACTION_LOG_PER_ORIG,
["DNS_label_len_gt_name_len"] = ACTION_LOG_PER_ORIG,
["DNS_label_len_gt_pkt"] = ACTION_LOG_PER_ORIG,
["DNS_label_too_long"] = ACTION_LOG_PER_ORIG,
["DNS_truncated_RR_rdlength_lt_len"] = ACTION_LOG,
["DNS_truncated_ans_too_short"] = ACTION_LOG,
["DNS_truncated_len_lt_hdr_len"] = ACTION_LOG,
["DNS_truncated_quest_too_short"] = ACTION_LOG,
["excessive_data_without_further_acks"] = ACTION_LOG,
["excess_RPC"] = ACTION_LOG_PER_ORIG,
["FIN_advanced_last_seq"] = ACTION_LOG,
["FIN_after_reset"] = ACTION_IGNORE,
["FIN_storm"] = ACTION_NOTICE_PER_ORIG,
["HTTP_bad_chunk_size"] = ACTION_LOG,
["HTTP_chunked_transfer_for_multipart_message"] = ACTION_LOG,
["HTTP_overlapping_messages"] = ACTION_LOG,
["unknown_HTTP_method"] = ACTION_LOG,
["HTTP_version_mismatch"] = ACTION_LOG,
["ident_request_addendum"] = ACTION_LOG,
["inappropriate_FIN"] = ACTION_LOG,
["inflate_failed"] = ACTION_LOG,
["invalid_irc_global_users_reply"] = ACTION_LOG,
["irc_invalid_command"] = ACTION_LOG,
["irc_invalid_dcc_message_format"] = ACTION_LOG,
["irc_invalid_invite_message_format"] = ACTION_LOG,
["irc_invalid_join_line"] = ACTION_LOG,
["irc_invalid_kick_message_format"] = ACTION_LOG,
["irc_invalid_line"] = ACTION_LOG,
["irc_invalid_mode_message_format"] = ACTION_LOG,
["irc_invalid_names_line"] = ACTION_LOG,
["irc_invalid_njoin_line"] = ACTION_LOG,
["irc_invalid_notice_message_format"] = ACTION_LOG,
["irc_invalid_oper_message_format"] = ACTION_LOG,
["irc_invalid_privmsg_message_format"] = ACTION_LOG,
["irc_invalid_reply_number"] = ACTION_LOG,
["irc_invalid_squery_message_format"] = ACTION_LOG,
["irc_invalid_topic_reply"] = ACTION_LOG,
["irc_invalid_who_line"] = ACTION_LOG,
["irc_invalid_who_message_format"] = ACTION_LOG,
["irc_invalid_whois_channel_line"] = ACTION_LOG,
["irc_invalid_whois_message_format"] = ACTION_LOG,
["irc_invalid_whois_operator_line"] = ACTION_LOG,
["irc_invalid_whois_user_line"] = ACTION_LOG,
["irc_line_size_exceeded"] = ACTION_LOG,
["irc_line_too_short"] = ACTION_LOG,
["irc_too_many_invalid"] = ACTION_LOG,
["line_terminated_with_single_CR"] = ACTION_LOG,
["line_terminated_with_single_LF"] = ACTION_LOG,
["malformed_ssh_identification"] = ACTION_LOG,
["malformed_ssh_version"] = ACTION_LOG,
["multiple_HTTP_request_elements"] = ACTION_LOG,
["NUL_in_line"] = ACTION_LOG,
["originator_RPC_reply"] = ACTION_LOG_PER_ORIG,
["partial_finger_request"] = ACTION_LOG,
["partial_ftp_request"] = ACTION_LOG,
["partial_ident_request"] = ACTION_LOG,
["partial_RPC"] = ACTION_LOG_PER_ORIG,
["pending_data_when_closed"] = ACTION_LOG,
["pop3_bad_base64_encoding"] = ACTION_LOG,
["pop3_client_command_unknown"] = ACTION_LOG,
["pop3_client_sending_server_commands"] = ACTION_LOG,
["pop3_malformed_auth_plain"] = ACTION_LOG,
["pop3_server_command_unknown"] = ACTION_LOG,
["pop3_server_sending_client_commands"] = ACTION_LOG,
["possible_split_routing"] = ACTION_LOG,
["premature_connection_reuse"] = ACTION_LOG,
["repeated_SYN_reply_wo_ack"] = ACTION_LOG,
["repeated_SYN_with_ack"] = ACTION_LOG,
["responder_RPC_call"] = ACTION_LOG_PER_ORIG,
["rlogin_text_after_rejected"] = ACTION_LOG,
["RPC_rexmit_inconsistency"] = ACTION_LOG,
["RPC_underflow"] = ACTION_LOG,
["RST_storm"] = ACTION_LOG,
["RST_with_data"] = ACTION_LOG,
["SSL_many_server_names"] = ACTION_LOG,
["simultaneous_open"] = ACTION_LOG_PER_CONN,
["spontaneous_FIN"] = ACTION_IGNORE,
["spontaneous_RST"] = ACTION_IGNORE,
["SMB_parsing_error"] = ACTION_LOG,
["no_smb_session_using_parsesambamsg"] = ACTION_LOG,
["smb_andx_command_failed_to_parse"] = ACTION_LOG,
["transaction_subcmd_missing"] = ACTION_LOG,
["successful_RPC_reply_to_invalid_request"] = ACTION_NOTICE_PER_ORIG,
["SYN_after_close"] = ACTION_LOG,
["SYN_after_partial"] = ACTION_NOTICE_PER_ORIG,
["SYN_after_reset"] = ACTION_LOG,
["SYN_inside_connection"] = ACTION_LOG,
["SYN_seq_jump"] = ACTION_LOG,
["SYN_with_data"] = ACTION_LOG_PER_ORIG,
["TCP_christmas"] = ACTION_LOG,
["truncated_ARP"] = ACTION_LOG,
["truncated_NTP"] = ACTION_LOG,
["UDP_datagram_length_mismatch"] = ACTION_LOG_PER_ORIG,
["unexpected_client_HTTP_data"] = ACTION_LOG,
["unexpected_multiple_HTTP_requests"] = ACTION_LOG,
["unexpected_server_HTTP_data"] = ACTION_LOG,
["unmatched_HTTP_reply"] = ACTION_LOG,
["unpaired_RPC_response"] = ACTION_LOG,
["window_recision"] = ACTION_LOG,
["double_%_in_URI"] = ACTION_LOG,
["illegal_%_at_end_of_URI"] = ACTION_LOG,
["unescaped_%_in_URI"] = ACTION_LOG,
["unescaped_special_URI_char"] = ACTION_LOG,
["deficit_netbios_hdr_len"] = ACTION_LOG,
["excess_netbios_hdr_len"] = ACTION_LOG,
["netbios_client_session_reply"] = ACTION_LOG,
["netbios_raw_session_msg"] = ACTION_LOG,
["netbios_server_session_request"] = ACTION_LOG,
["unknown_netbios_type"] = ACTION_LOG,
["excessively_large_fragment"] = ACTION_LOG,
["excessively_small_fragment"] = ACTION_LOG_PER_ORIG,
["fragment_inconsistency"] = ACTION_LOG_PER_ORIG,
["fragment_overlap"] = ACTION_LOG_PER_ORIG,
["fragment_protocol_inconsistency"] = ACTION_LOG,
["fragment_size_inconsistency"] = ACTION_LOG_PER_ORIG,
# These do indeed happen!
["fragment_with_DF"] = ACTION_LOG,
["incompletely_captured_fragment"] = ACTION_LOG,
["bad_IP_checksum"] = ACTION_LOG_PER_ORIG,
["bad_TCP_header_len"] = ACTION_LOG,
["internally_truncated_header"] = ACTION_LOG,
["truncated_IP"] = ACTION_LOG,
["truncated_header"] = ACTION_LOG,
} &default=ACTION_LOG &redef;
## To completely ignore a specific weird for a host, add the host
## and weird name into this set.
option ignore_hosts: set[addr, string] = {};
## Don't ignore repeats for weirds in this set. For example,
## it's handy keeping track of clustered checksum errors.
option weird_do_not_ignore_repeats = {
"bad_IP_checksum", "bad_TCP_checksum", "bad_UDP_checksum",
"bad_ICMP_checksum",
};
## This table is used to track identifier and name pairs that should be
## temporarily ignored because the problem has already been reported.
## This helps reduce the volume of high volume weirds by only allowing
## a unique weird every ``create_expire`` interval.
global weird_ignore: set[string, string] &create_expire=10min &redef;
## A state set which tracks unique weirds solely by name to reduce
## duplicate logging. This is deliberately not synchronized because it
## could cause overload during storms.
global did_log: set[string, string] &create_expire=1day &redef;
## A state set which tracks unique weirds solely by name to reduce
## duplicate notices from being raised.
global did_notice: set[string, string] &create_expire=1day &redef;
## Handlers of this event are invoked once per write to the weird
## logging stream before the data is actually written.
##
## rec: The weird columns about to be logged to the weird stream.
global log_weird: event(rec: Info);
global weird: function(w: Weird::Info);
}
# These actions result in the output being limited and further redundant
# weirds not progressing to being logged or noticed.
const limiting_actions = {
ACTION_LOG_ONCE,
ACTION_LOG_PER_CONN,
ACTION_LOG_PER_ORIG,
ACTION_NOTICE_ONCE,
ACTION_NOTICE_PER_CONN,
ACTION_NOTICE_PER_ORIG,
};
# This is an internal set to track which Weird::Action values lead to notice
# creation.
const notice_actions = {
ACTION_NOTICE,
ACTION_NOTICE_PER_CONN,
ACTION_NOTICE_PER_ORIG,
ACTION_NOTICE_ONCE,
};
event zeek_init() &priority=5
{
Log::create_stream(Weird::LOG, [$columns=Info, $ev=log_weird, $path="weird"]);
}
function flow_id_string(src: addr, dst: addr): string
{
return fmt("%s -> %s", src, dst);
}
function weird(w: Weird::Info)
{
local action = actions[w$name];
local identifier = "";
if ( w?$identifier )
identifier = w$identifier;
else
{
if ( w?$id )
identifier = id_string(w$id);
}
# If this weird is to be ignored let's drop out of here very early.
if ( action == ACTION_IGNORE || [w$name, identifier] in weird_ignore )
return;
if ( w?$conn )
{
w$uid = w$conn$uid;
w$id = w$conn$id;
}
if ( w?$id )
{
if ( [w$id$orig_h, w$name] in ignore_hosts ||
[w$id$resp_h, w$name] in ignore_hosts )
return;
}
if ( action in limiting_actions )
{
local notice_identifier = identifier;
if ( action in notice_actions )
{
# Handle notices
if ( w?$id && action == ACTION_NOTICE_PER_ORIG )
notice_identifier = fmt("%s", w$id$orig_h);
else if ( action == ACTION_NOTICE_ONCE )
notice_identifier = "";
# If this weird was already noticed then we're done.
if ( [w$name, notice_identifier] in did_notice )
return;
add did_notice[w$name, notice_identifier];
}
else
{
# Handle logging.
if ( w?$id && action == ACTION_LOG_PER_ORIG )
notice_identifier = fmt("%s", w$id$orig_h);
else if ( action == ACTION_LOG_ONCE )
notice_identifier = "";
# If this weird was already logged then we're done.
if ( [w$name, notice_identifier] in did_log )
return;
add did_log[w$name, notice_identifier];
}
}
if ( action in notice_actions )
{
w$notice = T;
local n: Notice::Info;
n$note = Activity;
n$msg = w$name;
if ( w?$conn )
n$conn = w$conn;
else
{
if ( w?$uid )
n$uid = w$uid;
if ( w?$id )
n$id = w$id;
}
if ( w?$addl )
n$sub = w$addl;
NOTICE(n);
}
# This is for the temporary ignoring to reduce volume for identical weirds.
if ( w$name !in weird_do_not_ignore_repeats )
add weird_ignore[w$name, identifier];
Log::write(Weird::LOG, w);
}
# The following events come from core generated weirds typically.
event conn_weird(name: string, c: connection, addl: string)
{
local i = Info($ts=network_time(), $name=name, $conn=c, $identifier=id_string(c$id));
if ( addl != "" )
i$addl = addl;
weird(i);
}
event flow_weird(name: string, src: addr, dst: addr, addl: string)
{
# We add the source and destination as port 0/unknown because that is
# what fits best here.
local id = conn_id($orig_h=src, $orig_p=count_to_port(0, unknown_transport),
$resp_h=dst, $resp_p=count_to_port(0, unknown_transport));
local i = Info($ts=network_time(), $name=name, $id=id, $identifier=flow_id_string(src,dst));
if ( addl != "" )
i$addl = addl;
weird(i);
}
event net_weird(name: string, addl: string)
{
local i = Info($ts=network_time(), $name=name);
if ( addl != "" )
i$addl = addl;
weird(i);
}
event file_weird(name: string, f: fa_file, addl: string)
{
local i = Info($ts=network_time(), $name=name, $addl=f$id);
if ( addl != "" )
i$addl += fmt(": %s", addl);
weird(i);
}
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