How to see alerts generated by preprocessors?

[Benjamin Wagrocki <Benjamin.Wagrocki () gmx de>]

Hello,

I am a new snort user and I am having some problems to see alerts which 
should be generated by the preprocessors. I simply do not see any event 
on the console. (alarms generated by the detectionengine and the 
signaturrules are working fine)

For instance my smtp_preprocessor config looks like this:
preprocessor smtp: \
ports { 25 587 691 } \
inspection_type stateful \
normalize cmds \
normalize_cmds { EXPN VRFY RCPT } \
alt_max_command_line_len 2 { MAIL } \
alt_max_command_line_len 300 { RCPT } \
alt_max_command_line_len 500 { HELP HELO ETRN } \
alt_max_command_line_len 255 { EXPN VRFY } \
invalid_cmds { HELP } \
alert_unknown_cmds

As you can see, the MAIL command may only be 2 characters long and the 
command HELP is not allowed.

But when I do a telnet connection over port 25 to a mailserver, and then 
use a longer mail from command or the help command no alerts are generated!

I am running snort 2.8.3.2 on CentOS5. I also tried snort on windows xp.

Snort is started this way:
snort -A console -c /etc/snort.conf -l /root/snortlog/ -k ascii

Here is my whole snort.conf:

#--------------------------------------------------
# http://www.snort.org Snort 2.8.3.2 Ruleset
# Contact: snort-sigs () lists sourceforge net
#--------------------------------------------------
# $Id$
#
###################################################
# This file contains a sample snort configuration.
# You can take the following steps to create your own custom configuration:
#
# 1) Set the variables for your network
# 2) Configure dynamic loaded libraries
# 3) Configure preprocessors
# 4) Configure output plugins
# 5) Add any runtime config directives
# 6) Customize your rule set
#
###################################################
# Step #1: Set the network variables:
#
# You must change the following variables to reflect your local network. 
The
# variable is currently setup for an RFC 1918 address space.
#
# You can specify it explicitly as:
#
# var HOME_NET 10.1.1.0/24
#
# or use global variable $_ADDRESS which will be always
# initialized to IP address and netmask of the network interface which 
you run
# snort at. Under Windows, this must be specified as
# $(_ADDRESS), such as:
# $(\Device\Packet_{12345678-90AB-CDEF-1234567890AB}_ADDRESS)
#
# var HOME_NET $eth0_ADDRESS
#
# You can specify lists of IP addresses for HOME_NET
# by separating the IPs with commas like this:
#
# var HOME_NET [10.1.1.0/24,192.168.1.0/24]
#
# MAKE SURE YOU DON'T PLACE ANY SPACES IN YOUR LIST!
#
# or you can specify the variable to be any IP address
# like this:

var HOME_NET any

# Set up the external network addresses as well. A good start may be "any"
var EXTERNAL_NET any

# Configure your server lists. This allows snort to only look for 
attacks to
# systems that have a service up. Why look for HTTP attacks if you are not
# running a web server? This allows quick filtering based on IP addresses
# These configurations MUST follow the same configuration scheme as defined
# above for $HOME_NET.

# List of DNS servers on your network
var DNS_SERVERS $HOME_NET

# List of SMTP servers on your network
var SMTP_SERVERS $HOME_NET

# List of web servers on your network
var HTTP_SERVERS $HOME_NET

# List of sql servers on your network
var SQL_SERVERS $HOME_NET

# List of telnet servers on your network
var TELNET_SERVERS $HOME_NET

# List of snmp servers on your network
var SNMP_SERVERS $HOME_NET

# Configure your service ports. This allows snort to look for attacks 
destined
# to a specific application only on the ports that application runs on. For
# example, if you run a web server on port 8081, set your HTTP_PORTS 
variable
# like this:
#
# portvar HTTP_PORTS 8081
#
# Ports you run web servers on
portvar HTTP_PORTS 80

# NOTE: If you wish to define multiple HTTP ports, use the portvar
# syntax to represent lists of ports and port ranges. Examples:
## portvar HTTP_PORTS [80,8080]
## portvar HTTP_PORTS [80,8000:8080]
# And only include the rule that uses $HTTP_PORTS once.
#
# The pre-2.8.0 approach of redefining the variable to a different port and
# including the rules file twice is obsolete. See README.variables for more
# details.

# Ports you want to look for SHELLCODE on.
portvar SHELLCODE_PORTS !80

# Ports you might see oracle attacks on
portvar ORACLE_PORTS 1521

# other variables
#
# AIM servers. AOL has a habit of adding new AIM servers, so instead of
# modifying the signatures when they do, we add them to this list of 
servers.
var AIM_SERVERS 
[64.12.24.0/23,64.12.28.0/23,64.12.161.0/24,64.12.163.0/24,64.12.200.0/24,205.188.3.0/24,205.188.5.0/24,205.188.7.0/24,205.188.9.0/24,205.188.153.0/24,205.188.179.0/24,205.188.248.0/24]
 


# Path to your rules files (this can be a relative path)
# Note for Windows users: You are advised to make this an absolute path,
# such as: c:\snort\rules
var RULE_PATH /etc/snort/rules
var PREPROC_RULE_PATH ../preproc_rules

# Configure the snort decoder
# ============================
#
# Snort's decoder will alert on lots of things such as header
# truncation or options of unusual length or infrequently used tcp options
#
#
# Stop generic decode events:
#
# config disable_decode_alerts
#
# Stop Alerts on experimental TCP options
#
# config disable_tcpopt_experimental_alerts
#
# Stop Alerts on obsolete TCP options
#
# config disable_tcpopt_obsolete_alerts
#
# Stop Alerts on T/TCP alerts
#
# In snort 2.0.1 and above, this only alerts when a TCP option is detected
# that shows T/TCP being actively used on the network. If this is normal
# behavior for your network, disable the next option.
#
# config disable_tcpopt_ttcp_alerts
#
# Stop Alerts on all other TCPOption type events:
#
# config disable_tcpopt_alerts
#
# Stop Alerts on invalid ip options
#
# config disable_ipopt_alerts
#
# Alert if value in length field (IP, TCP, UDP) is greater than the
# actual length of the captured portion of the packet that the length
# is supposed to represent:
#
# config enable_decode_oversized_alerts
#
# Same as above, but drop packet if in Inline mode -
# enable_decode_oversized_alerts must be enabled for this to work:
#
# config enable_decode_oversized_drops
#

# Configure the detection engine
# ===============================
#
# Use a different pattern matcher in case you have a machine with very 
limited
# resources:
#
# config detection: search-method lowmem

# Configure Inline Resets
# ========================
#
# If running an iptables firewall with snort in InlineMode() we can now
# perform resets via a physical device. We grab the indev from iptables
# and use this for the interface on which to send resets. This config
# option takes an argument for the src mac address you want to use in the
# reset packet. This way the bridge can remain stealthy. If the src mac
# option is not set we use the mac address of the indev device. If we
# don't set this option we will default to sending resets via raw socket,
# which needs an ipaddress to be assigned to the int.
#
# config layer2resets: 00:06:76:DD:5F:E3

###################################################
# Step #2: Configure dynamic loaded libraries
#
# If snort was configured to use dynamically loaded libraries,
# those libraries can be loaded here.
#
# Each of the following configuration options can be done via
# the command line as well.
#
# Load all dynamic preprocessors from the install path
# (same as command line option --dynamic-preprocessor-lib-dir)
#
dynamicpreprocessor directory /usr/lib/snort-2.8.3.2_dynamicpreprocessor/
#
# Load a specific dynamic preprocessor library from the install path
# (same as command line option --dynamic-preprocessor-lib)
#
# dynamicpreprocessor file 
/usr/local/lib/snort_dynamicpreprocessor/libdynamicexample.so
#
# Load a dynamic engine from the install path
# (same as command line option --dynamic-engine-lib)
#
dynamicengine /usr/lib/snort-2.8.3.2_dynamicengine/libsf_engine.so
#
# Load all dynamic rules libraries from the install path
# (same as command line option --dynamic-detection-lib-dir)
#
# dynamicdetection directory /usr/local/lib/snort_dynamicrule/
#
# Load a specific dynamic rule library from the install path
# (same as command line option --dynamic-detection-lib)
#
# dynamicdetection file 
/usr/local/lib/snort_dynamicrule/libdynamicexamplerule.so
#

###################################################
# Step #3: Configure preprocessors
#
# General configuration for preprocessors is of
# the form
# preprocessor :

# Configure Flow tracking module
# -------------------------------
#
# The Flow tracking module is meant to start unifying the state keeping
# mechanisms of snort into a single place. Right now, only a portscan 
detector
# is implemented but in the long term, many of the stateful subsystems of
# snort will be migrated over to becoming flow plugins. This must be 
enabled
# for flow-portscan to work correctly.
#
# See README.flow for additional information
#
#preprocessor flow: stats_interval 0 hash 2

# frag3: Target-based IP defragmentation
# --------------------------------------
#
# Frag3 is a brand new IP defragmentation preprocessor that is capable of
# performing "target-based" processing of IP fragments. Check out the
# README.frag3 file in the doc directory for more background and 
configuration
# information.
#
# Frag3 configuration is a two step process, a global initialization phase
# followed by the definition of a set of defragmentation engines.
#
# Global configuration defines the number of fragmented packets that 
Snort can
# track at the same time and gives you options regarding the memory cap 
for the
# subsystem or, optionally, allows you to preallocate all the memory for 
the
# entire frag3 system.
#
# frag3_global options:
# max_frags: Maximum number of frag trackers that may be active at once.
# Default value is 8192.
# memcap: Maximum amount of memory that frag3 may access at any given time.
# Default value is 4MB.
# prealloc_frags: Maximum number of individual fragments that may be 
processed
# at once. This is instead of the memcap system, uses static
# allocation to increase performance. No default value. Each
# preallocated fragment typically eats ~1550 bytes. However,
# the exact amount is determined by the snaplen, and this can
# go as high as 64K so beware!
#
# Target-based behavior is attached to an engine as a "policy" for handling
# overlaps and retransmissions as enumerated in the Paxson paper. There are
# currently five policy types available: "BSD", "BSD-right", "First", 
"Linux"
# and "Last". Engines can be bound to standard Snort CIDR blocks or
# IP lists.
#
# frag3_engine options:
# timeout: Amount of time a fragmented packet may be active before 
expiring.
# Default value is 60 seconds.
# ttl_limit: Limit of delta allowable for TTLs of packets in the fragments.
# Based on the initial received fragment TTL.
# min_ttl: Minimum acceptable TTL for a fragment, frags with TTLs below 
this
# value will be discarded. Default value is 0.
# detect_anomalies: Activates frag3's anomaly detection mechanisms.
# policy: Target-based policy to assign to this engine. Default is BSD.
# bind_to: IP address set to bind this engine to. Default is all hosts.
#
# Frag3 configuration example:
#preprocessor frag3_global: max_frags 65536, prealloc_frags 65536
#preprocessor frag3_engine: policy linux \
# bind_to [10.1.1.12/32,10.1.1.13/32] \
# detect_anomalies
#preprocessor frag3_engine: policy first \
# bind_to 10.2.1.0/24 \
# detect_anomalies
#preprocessor frag3_engine: policy last \
# bind_to 10.3.1.0/24
#preprocessor frag3_engine: policy bsd

preprocessor frag3_global: max_frags 65536
preprocessor frag3_engine: policy first detect_anomalies


# stream4: stateful inspection/stream reassembly for Snort
#----------------------------------------------------------------------
# Use in concert with the -z [all|est] command line switch to defeat 
stick/snot
# against TCP rules. Also performs full TCP stream reassembly, stateful
# inspection of TCP streams, etc. Can statefully detect various portscan
# types, fingerprinting, ECN, etc.

# stateful inspection directive
# no arguments loads the defaults (timeout 30, memcap 838860Cool
# options (options are comma delimited):
# detect_scans - stream4 will detect stealth portscans and generate alerts
# when it sees them when this option is set
# detect_state_problems - detect TCP state problems, this tends to be very
# noisy because there are a lot of crappy ip stack
# implementations out there
#
# disable_evasion_alerts - turn off the possibly noisy mitigation of
# overlapping sequences.
#
# ttl_limit [number] - differential of the initial ttl on a session versus
# the normal that someone may be playing games.
# Routing flap may cause lots of false positives.
#
# keepstats [machine|binary] - keep session statistics, add "machine" to
# get them in a flat format for machine reading, add
# "binary" to get them in a unified binary output
# format
# noinspect - turn off stateful inspection only
# timeout [number] - set the session timeout counter to [number] seconds,
# default is 30 seconds
# max_sessions [number] - limit the number of sessions stream4 keeps
# track of
# memcap [number] - limit stream4 memory usage to [number] bytes (does
# not include session tracking, which is set by the
# max_sessions option)
# log_flushed_streams - if an event is detected on a stream this option 
will
# cause all packets that are stored in the stream4
# packet buffers to be flushed to disk. This only
# works when logging in pcap mode!
# server_inspect_limit [bytes] - Byte limit on server side inspection.
# enable_udp_sessions - turn on tracking of "sessions" over UDP. Requires
# configure --enable-stream4udp. UDP sessions are
# only created when there is a rule for the sender or
# responder that has a flow or flowbits keyword.
# max_udp_sessions [number] - limit the number of simultaneous UDP sessions
# to track
# udp_ignore_any - Do not inspect UDP packets unless there is a port 
specific
# rule for a given port. This is a performance improvement
# and turns off inspection for udp xxx any -> xxx any rules
# cache_clean_sessions [number] - Cleanup the session cache by number 
sessions
# at a time. The larger the value, the
# more sessions are purged from the cache when
# the session limit or memcap is reached.
# Defaults to 5.
#
#
#
# Stream4 uses Generator ID 111 and uses the following SIDS
# for that GID:
# SID Event description
# ----- -------------------
# 1 Stealth activity
# 2 Evasive RST packet
# 3 Evasive TCP packet retransmission
# 4 TCP Window violation
# 5 Data on SYN packet
# 6 Stealth scan: full XMAS
# 7 Stealth scan: SYN-ACK-PSH-URG
# 8 Stealth scan: FIN scan
# 9 Stealth scan: NULL scan
# 10 Stealth scan: NMAP XMAS scan
# 11 Stealth scan: Vecna scan
# 12 Stealth scan: NMAP fingerprint scan stateful detect
# 13 Stealth scan: SYN-FIN scan
# 14 TCP forward overlap

#preprocessor stream4: disable_evasion_alerts

# tcp stream reassembly directive
# no arguments loads the default configuration
# Only reassemble the client,
# Only reassemble the default list of ports (See below),
# Give alerts for "bad" streams
#
# Available options (comma delimited):
# clientonly - reassemble traffic for the client side of a connection only
# serveronly - reassemble traffic for the server side of a connection only
# both - reassemble both sides of a session
# noalerts - turn off alerts from the stream reassembly stage of stream4
# ports [list] - use the space separated list of ports in [list], "all"
# will turn on reassembly for all ports, "default" will turn
# on reassembly for ports 21, 23, 25, 42, 53, 80, 110,
# 111, 135, 136, 137, 139, 143, 445, 513, 514, 1433, 1521,
# 2401, and 3306
# favor_old - favor an old segment (based on sequence number) over a new 
one.
# This is the default.
# favor_new - favor an new segment (based on sequence number) over an 
old one.
# overlap_limit [number] - limit on overlaping segments for a session.
# flush_on_alert - flushes stream when an alert is generated for a session.
# flush_behavior [mode] -
# default - use old static flushpoints (default)
# large_window - use new larger static flushpoints
# random - use random flushpoints defined by flush_base,
# flush_seed and flush_range
# flush_base [number] - lowest allowed random flushpoint (512 by default)
# flush_range [number] - number is the space within which random 
flushpoints
# are generated (default 1213)
# flush_seed [number] - seed for the random number generator, defaults to
# Snort PID + time
#
# Using the default random flushpoints, the smallest flushpoint is 512,
# and the largest is 1725 bytes.
#preprocessor stream4_reassemble

# stream5: Target Based stateful inspection/stream reassembly for Snort
# ---------------------------------------------------------------------
# Stream5 is a target-based stream engine for Snort. Its functionality
# replaces that of Stream4. Consequently, BOTH Stream4 and Stream5
# cannot be used simultaneously. Comment out the stream4 configurations
# above to use Stream5.
#
# See README.stream5 for details on the configuration options.
#
# Example config (that emulates Stream4 with UDP support compiled in)
preprocessor stream5_global: max_tcp 8192, track_tcp yes, \
track_udp no
preprocessor stream5_tcp: policy first, use_static_footprint_sizes
# preprocessor stream5_udp: ignore_any_rules


# Performance Statistics
# ----------------------
# Documentation for this is provided in the Snort Manual. You should 
read it.
# It is included in the release distribution as doc/snort_manual.pdf
#
# preprocessor perfmonitor: time 300 file /var/snort/snort.stats pktcnt 
10000

# http_inspect: normalize and detect HTTP traffic and protocol anomalies
#
# lots of options available here. See doc/README.http_inspect.
# unicode.map should be wherever your snort.conf lives, or given
# a full path to where snort can find it.
preprocessor http_inspect: global \
iis_unicode_map unicode.map 1252

preprocessor http_inspect_server: server default \
profile all ports { 80 8080 8180 } oversize_dir_length 500

#
# Example unique server configuration
#
#preprocessor http_inspect_server: server 1.1.1.1 \
# ports { 80 3128 8080 } \
# server_flow_depth 0 \
# ascii no \
# double_decode yes \
# non_rfc_char { 0x00 } \
# chunk_length 500000 \
# non_strict \
# oversize_dir_length 300 \
# no_alerts


# rpc_decode: normalize RPC traffic
# ---------------------------------
# RPC may be sent in alternate encodings besides the usual 4-byte encoding
# that is used by default. This plugin takes the port numbers that RPC
# services are running on as arguments - it is assumed that the given ports
# are actually running this type of service. If not, change the ports or 
turn
# it off.
# The RPC decode preprocessor uses generator ID 106
#
# arguments: space separated list
# alert_fragments - alert on any rpc fragmented TCP data
# no_alert_multiple_requests - don't alert when >1 rpc query is in a packet
# no_alert_large_fragments - don't alert when the fragmented
# sizes exceed the current packet size
# no_alert_incomplete - don't alert when a single segment
# exceeds the current packet size

preprocessor rpc_decode: 111 32771

# bo: Back Orifice detector
# -------------------------
# Detects Back Orifice traffic on the network.
#
# arguments:
# syntax:
# preprocessor bo: noalert { client | server | general | snort_attack } \
# drop { client | server | general | snort_attack }
# example:
# preprocessor bo: noalert { general server } drop { snort_attack }
#
#
# The Back Orifice detector uses Generator ID 105 and uses the
# following SIDS for that GID:
# SID Event description
# ----- -------------------
# 1 Back Orifice traffic detected
# 2 Back Orifice Client Traffic Detected
# 3 Back Orifice Server Traffic Detected
# 4 Back Orifice Snort Buffer Attack

preprocessor bo

# ftp_telnet: FTP & Telnet normalizer, protocol enforcement and buff 
overflow
# 
---------------------------------------------------------------------------
# This preprocessor normalizes telnet negotiation strings from telnet and
# ftp traffic. It looks for traffic that breaks the normal data stream
# of the protocol, replacing it with a normalized representation of that
# traffic so that the "content" pattern matching keyword can work without
# requiring modifications.
#
# It also performs protocol correctness checks for the FTP command channel,
# and identifies open FTP data transfers.
#
# FTPTelnet has numerous options available, please read
# README.ftptelnet for help configuring the options for the global
# telnet, ftp server, and ftp client sections for the protocol.

#####
# Per Step #2, set the following to load the ftptelnet preprocessor
# dynamicpreprocessor file
# or use commandline option
# --dynamic-preprocessor-lib

preprocessor ftp_telnet: global \
encrypted_traffic yes \
inspection_type stateful

preprocessor ftp_telnet_protocol: telnet \
normalize \
ayt_attack_thresh 200

# This is consistent with the FTP rules as of 18 Sept 2004.
# CWD can have param length of 200
# MODE has an additional mode of Z (compressed)
# Check for string formats in USER & PASS commands
# Check nDTM commands that set modification time on the file.
preprocessor ftp_telnet_protocol: ftp server default \
def_max_param_len 100 \
alt_max_param_len 200 { CWD } \
cmd_validity MODE < char ASBCZ > \
cmd_validity MDTM < [ date nnnnnnnnnnnnnn[.n[n[n]]] ] string > \
chk_str_fmt { USER PASS RNFR RNTO SITE MKD } \
telnet_cmds yes \
data_chan

preprocessor ftp_telnet_protocol: ftp client default \
max_resp_len 256 \
bounce yes \
telnet_cmds yes

# smtp: SMTP normalizer, protocol enforcement and buffer overflow
# 
---------------------------------------------------------------------------
# This preprocessor normalizes SMTP commands by removing extraneous spaces.
# It looks for overly long command lines, response lines, and data 
header lines.
# It can alert on invalid commands, or specific valid commands. It can 
optionally
# ignore mail data, and can ignore TLS encrypted data.
#
# SMTP has numerous options available, please read README.SMTP for help
# configuring options.

#####
# Per Step #2, set the following to load the smtp preprocessor
# dynamicpreprocessor file
# or use commandline option
# --dynamic-preprocessor-lib

preprocessor smtp: \
ports { 25 587 691 } \
inspection_type stateful \
normalize cmds \
normalize_cmds { EXPN VRFY RCPT } \
alt_max_command_line_len 2 { MAIL } \
alt_max_command_line_len 300 { RCPT } \
alt_max_command_line_len 500 { HELP HELO ETRN } \
alt_max_command_line_len 255 { EXPN VRFY } \
invalid_cmds { HELP } \
alert_unknown_cmds

# sfPortscan
# ----------
# Portscan detection module. Detects various types of portscans and
# portsweeps. For more information on detection philosophy, alert types,
# and detailed portscan information, please refer to the README.sfportscan.
#
# -configuration options-
# proto { tcp udp icmp ip all }
# The arguments to the proto option are the types of protocol scans that
# the user wants to detect. Arguments should be separated by spaces and
# not commas.
# scan_type { portscan portsweep decoy_portscan distributed_portscan all }
# The arguments to the scan_type option are the scan types that the
# user wants to detect. Arguments should be separated by spaces and not
# commas.
# sense_level { low|medium|high }
# There is only one argument to this option and it is the level of
# sensitivity in which to detect portscans. The 'low' sensitivity
# detects scans by the common method of looking for response errors, such
# as TCP RSTs or ICMP unreachables. This level requires the least
# tuning. The 'medium' sensitivity level detects portscans and
# filtered portscans (portscans that receive no response). This
# sensitivity level usually requires tuning out scan events from NATed
# IPs, DNS cache servers, etc. The 'high' sensitivity level has
# lower thresholds for portscan detection and a longer time window than
# the 'medium' sensitivity level. Requires more tuning and may be noisy
# on very active networks. However, this sensitivity levels catches the
# most scans.
# memcap { positive integer }
# The maximum number of bytes to allocate for portscan detection. The
# higher this number the more nodes that can be tracked.
# logfile { filename }
# This option specifies the file to log portscan and detailed portscan
# values to. If there is not a leading /, then snort logs to the
# configured log directory. Refer to README.sfportscan for details on
# the logged values in the logfile.
# watch_ip { Snort IP List }
# ignore_scanners { Snort IP List }
# ignore_scanned { Snort IP List }
# These options take a snort IP list as the argument. The 'watch_ip'
# option specifies the IP(s) to watch for portscan. The
# 'ignore_scanners' option specifies the IP(s) to ignore as scanners.
# Note that these hosts are still watched as scanned hosts. The
# 'ignore_scanners' option is used to tune alerts from very active
# hosts such as NAT, nessus hosts, etc. The 'ignore_scanned' option
# specifies the IP(s) to ignore as scanned hosts. Note that these hosts
# are still watched as scanner hosts. The 'ignore_scanned' option is
# used to tune alerts from very active hosts such as syslog servers, etc.
# detect_ack_scans
# This option will include sessions picked up in midstream by the stream
# module, which is necessary to detect ACK scans. However, this can lead to
# false alerts, especially under heavy load with dropped packets; which 
is why
# the option is off by default.
#
preprocessor sfportscan: proto { all } \
memcap { 10000000 } \
sense_level { low }

# arpspoof
#----------------------------------------
# Experimental ARP detection code from Jeff Nathan, detects ARP attacks,
# unicast ARP requests, and specific ARP mapping monitoring. To make use of
# this preprocessor you must specify the IP and hardware address of 
hosts on
# the same layer 2 segment as you. Specify one host IP MAC combo per line.
# Also takes a "-unicast" option to turn on unicast ARP request detection.
# Arpspoof uses Generator ID 112 and uses the following SIDS for that GID:

# SID Event description
# ----- -------------------
# 1 Unicast ARP request
# 2 Etherframe ARP mismatch (src)
# 3 Etherframe ARP mismatch (dst)
# 4 ARP cache overwrite attack

#preprocessor arpspoof
#preprocessor arpspoof_detect_host: 192.168.40.1 f0:0f:00:f0:0f:00

# ssh
#----------------------------------------
# EXPERIMENTAL CODE!!!
#
# THIS CODE IS STILL EXPERIMENTAL AND MAY OR MAY NOT BE STABLE!
# USE AT YOUR OWN RISK! DO NOT USE IN PRODUCTION ENVIRONMENTS.
# YOU HAVE BEEN WARNED.
#
# The SSH preprocessor detects the following exploits: Gobbles, CRC 32,
# Secure CRT, and the Protocol Mismatch exploit.
#
# Both Gobbles and CRC 32 attacks occur after the key exchange, and are
# therefore encrypted. Both attacks involve sending a large payload
# (20kb+) to the server immediately after the authentication challenge.
# To detect the attacks, the SSH preprocessor counts the number of bytes
# transmitted to the server. If those bytes exceed a pre-defined limit
# within a pre-define number of packets, an alert is generated. Since
# Gobbles only effects SSHv2 and CRC 32 only effects SSHv1, the SSH
# version string exchange is used to distinguish the attacks.
#
# The Secure CRT and protocol mismatch exploits are observable before
# the key exchange.
#
# SSH has numerous options available, please read README.ssh for help
# configuring options.

#####
# Per Step #2, set the following to load the ssh preprocessor
# dynamicpreprocessor file
# or use commandline option
# --dynamic-preprocessor-lib
#
#preprocessor ssh: server_ports { 22 } \
# max_client_bytes 19600 \
# max_encrypted_packets 20

# DCE/RPC
#----------------------------------------
#
# The dcerpc preprocessor detects and decodes SMB and DCE/RPC traffic.
# It is primarily interested in DCE/RPC data, and only decodes SMB
# to get at the DCE/RPC data carried by the SMB layer.
#
# Currently, the preprocessor only handles reassembly of fragmentation
# at both the SMB and DCE/RPC layer. Snort rules can be evaded by
# using both types of fragmentation; with the preprocessor enabled
# the rules are given a buffer with a reassembled SMB or DCE/RPC
# packet to examine.
#
# At the SMB layer, only fragmentation using WriteAndX is currently
# reassembled. Other methods will be handled in future versions of
# the preprocessor.
#
# Autodetection of SMB is done by looking for "\xFFSMB" at the start of
# the SMB data, as well as checking the NetBIOS header (which is always
# present for SMB) for the type "SMB Session".
#
# Autodetection of DCE/RPC is not as reliable. Currently, two bytes are
# checked in the packet. Assuming that the data is a DCE/RPC header,
# one byte is checked for DCE/RPC version (5) and another for the type
# "DCE/RPC Request". If both match, the preprocessor proceeds with that
# assumption that it is looking at DCE/RPC data. If subsequent checks
# are nonsensical, it ends processing.
#
# DCERPC has numerous options available, please read README.dcerpc for help
# configuring options.

#####
# Per Step #2, set the following to load the dcerpc preprocessor
# dynamicpreprocessor file
# or use commandline option
# --dynamic-preprocessor-lib

preprocessor dcerpc: \
autodetect \
max_frag_size 3000 \
memcap 100000

# DNS
#----------------------------------------
# The dns preprocessor (currently) decodes DNS Response traffic
# and detects a few vulnerabilities.
#
# DNS has a few options available, please read README.dns for
# help configuring options.

#####
# Per Step #2, set the following to load the dns preprocessor
# dynamicpreprocessor file
# or use commandline option
# --dynamic-preprocessor-lib

preprocessor dns: \
ports { 53 } \
enable_rdata_overflow

# SSL
#----------------------------------------
# Encrypted traffic should be ignored by Snort for both performance reasons
# and to reduce false positives. The SSL Dynamic Preprocessor (SSLPP)
# inspects SSL traffic and optionally determines if and when to stop
# inspection of it.
#
# Typically, SSL is used over port 443 as HTTPS. By enabling the SSLPP to
# inspect port 443, only the SSL handshake of each connection will be
# inspected. Once the traffic is determined to be encrypted, no further
# inspection of the data on the connection is made.
#
# Important note: Stream4 or Stream5 should be explicitly told to 
reassemble
# traffic on the ports that you intend to inspect SSL
# encrypted traffic on.
#
# To add reassembly on port 443 to Stream5, use 'port both 443' in the
# Stream5 configuration.

preprocessor ssl: noinspect_encrypted


####################################################################
# Step #4: Configure output plugins
#
# Uncomment and configure the output plugins you decide to use. General
# configuration for output plugins is of the form:
#
# output :
#
# alert_syslog: log alerts to syslog
# ----------------------------------
# Use one or more syslog facilities as arguments. Win32 can also optionally
# specify a particular hostname/port. Under Win32, the default hostname is
# '127.0.0.1', and the default port is 514.
#
# [Unix flavours should use this format...]
# output alert_syslog: LOG_AUTH LOG_ALERT
#
# [Win32 can use any of these formats...]
# output alert_syslog: LOG_AUTH LOG_ALERT
# output alert_syslog: host=hostname, LOG_AUTH LOG_ALERT
# output alert_syslog: host=hostname:port, LOG_AUTH LOG_ALERT

# log_tcpdump: log packets in binary tcpdump format
# -------------------------------------------------
# The only argument is the output file name.
#
# output log_tcpdump: tcpdump.log

# database: log to a variety of databases
# ---------------------------------------
# See the README.database file for more information about configuring
# and using this plugin.
#
# output database: log, mysql, user=root password=test dbname=db 
host=localhost
# output database: alert, postgresql, user=snort dbname=snort
# output database: log, odbc, user=snort dbname=snort
# output database: log, mssql, dbname=snort user=snort password=test
# output database: log, oracle, dbname=snort user=snort password=test

# unified: Snort unified binary format alerting and logging
# -------------------------------------------------------------
# The unified output plugin provides two new formats for logging and 
generating
# alerts from Snort, the "unified" format. The unified format is a straight
# binary format for logging data out of Snort that is designed to be 
fast and
# efficient. Used with barnyard (the new alert/log processor), most of the
# overhead for logging and alerting to various slow storage mechanisms 
such as
# databases or the network can now be avoided.
#
# Check out the spo_unified.h file for the data formats.
#
# Two arguments are supported.
# filename - base filename to write to (current time_t is appended)
# limit - maximum size of spool file in MB (default: 12Cool
#
# output alert_unified: filename snort.alert, limit 128
# output log_unified: filename snort.log, limit 128


# prelude: log to the Prelude Hybrid IDS system
# ---------------------------------------------
#
# profile = Name of the Prelude profile to use (default is snort).
#
# Snort priority to IDMEF severity mappings:
# high < medium < low < info
#
# These are the default mapped from classification.config:
# info = 4
# low = 3
# medium = 2
# high = anything below medium
#
# output alert_prelude
# output alert_prelude: profile=snort-profile-name


# You can optionally define new rule types and associate one or more output
# plugins specifically to that type.
#
# This example will create a type that will log to just tcpdump.
# ruletype suspicious
# {
# type log
# output log_tcpdump: suspicious.log
# }
#
# EXAMPLE RULE FOR SUSPICIOUS RULETYPE:
# suspicious tcp $HOME_NET any -> $HOME_NET 6667 (msg:"Internal IRC 
Server"Wink
#
# This example will create a rule type that will log to syslog and a mysql
# database:
# ruletype redalert
# {
# type alert
# output alert_syslog: LOG_AUTH LOG_ALERT
# output database: log, mysql, user=snort dbname=snort host=localhost
# }
#
# EXAMPLE RULE FOR REDALERT RULETYPE:
# redalert tcp $HOME_NET any -> $EXTERNAL_NET 31337 \
# (msg:"Someone is being LEET"; flags:A+Wink

#
# Include classification & priority settings
# Note for Windows users: You are advised to make this an absolute path,
# such as: c:\snort\etc\classification.config
#

include classification.config

#
# Include reference systems
# Note for Windows users: You are advised to make this an absolute path,
# such as: c:\snort\etc\reference.config
#

include reference.config

####################################################################
# Step #5: Configure snort with config statements
#
# See the snort manual for a full set of configuration references
#
# config flowbits_size: 64
#
# New global ignore_ports config option from Andy Mullican
#
# config ignore_ports:
# config ignore_ports: tcp 21 6667:6671 1356
# config ignore_ports: udp 1:17 53


####################################################################
# Step #6: Customize your rule set
#
# Up to date snort rules are available at http://www.snort.org
#
# The snort web site has documentation about how to write your own 
custom snort
# rules.

#=========================================
# Include all relevant rulesets here
#
# The following rulesets are disabled by default:
#
# web-attacks, backdoor, shellcode, policy, porn, info, icmp-info, virus,
# chat, multimedia, and p2p
#
# These rules are either site policy specific or require tuning in order 
to not
# generate false positive alerts in most enviornments.
#
# Please read the specific include file for more information and
# README.alert_order for how rule ordering affects how alerts are 
triggered.
#=========================================

#include $RULE_PATH/local.rules
#include $RULE_PATH/bad-traffic.rules
#include $RULE_PATH/exploit.rules
#include $RULE_PATH/scan.rules
#include $RULE_PATH/finger.rules
#include $RULE_PATH/ftp.rules
#include $RULE_PATH/telnet.rules
#include $RULE_PATH/rpc.rules
#include $RULE_PATH/rservices.rules
#include $RULE_PATH/dos.rules
#include $RULE_PATH/ddos.rules
#include $RULE_PATH/dns.rules
#include $RULE_PATH/tftp.rules

#include $RULE_PATH/web-cgi.rules
#include $RULE_PATH/web-coldfusion.rules
#include $RULE_PATH/web-iis.rules
#include $RULE_PATH/web-frontpage.rules
#include $RULE_PATH/web-misc.rules
#include $RULE_PATH/web-client.rules
#include $RULE_PATH/web-php.rules

#include $RULE_PATH/sql.rules
#include $RULE_PATH/x11.rules
#include $RULE_PATH/icmp.rules
#include $RULE_PATH/netbios.rules
#include $RULE_PATH/misc.rules
#include $RULE_PATH/attack-responses.rules
#include $RULE_PATH/oracle.rules
#include $RULE_PATH/mysql.rules
#include $RULE_PATH/snmp.rules

#include $RULE_PATH/smtp.rules
#include $RULE_PATH/imap.rules
#include $RULE_PATH/pop2.rules
#include $RULE_PATH/pop3.rules

#include $RULE_PATH/nntp.rules
#include $RULE_PATH/other-ids.rules
# include $RULE_PATH/web-attacks.rules
# include $RULE_PATH/backdoor.rules
# include $RULE_PATH/shellcode.rules
# include $RULE_PATH/policy.rules
# include $RULE_PATH/porn.rules
# include $RULE_PATH/info.rules
# include $RULE_PATH/icmp-info.rules
# include $RULE_PATH/virus.rules
# include $RULE_PATH/chat.rules
# include $RULE_PATH/multimedia.rules
# include $RULE_PATH/p2p.rules
# include $RULE_PATH/spyware-put.rules
# include $RULE_PATH/specific-threats.rules
#include $RULE_PATH/experimental.rules
include $RULE_PATH/testing.rules

# include $PREPROC_RULE_PATH/preprocessor.rules
# include $PREPROC_RULE_PATH/decoder.rules

# Include any thresholding or suppression commands. See threshold.conf 
in the
# /etc directory for details. Commands don't necessarily need to be
# contained in this conf, but a separate conf makes it easier to 
maintain them.
# Note for Windows users: You are advised to make this an absolute path,
# such as: c:\snort\etc\threshold.conf
# Uncomment if needed.
# include threshold.conf

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