Snort Cheat Sheet

Many people prefer open source to buying enterprise products. The pro’s of enterprise include not having to build everything, threat feeds provided by vendor, vendor support tested deployments. The pro’s of open source are the cost savings (outside of time to build), customization options and for Snort, huge community support.

Comparitech provided a SNORT cheat sheet for those looking to go open source with their IPS/IDS needs. SNORT owned by Cisco is one of the leading open source IDS/IPS options out there. Many vendors use SNORT in the back end. Learn more about SNORT at https://www.snort.org/. The original post for the SNORT cheat sheet can be found at https://www.comparitech.com/net-admin/snort-cheat-sheet/. Here is the post from Comparitech.

All the tables provided in the cheat sheets are also presented in tables below which are easy to copy and paste.

The Snort Cheat Sheet covers:

  • Sniffer mode, Packet logger mode, and NIDS mode operation
  • Snort rules format
  • Logger mode command line options
  • NIDS mode options
  • Alert and rule examples

View or Download the Cheat Sheet JPG image

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View or Download the cheat sheet PDF file

Download the cheat sheet PDF file here. When it opens in a new browser tab, simply right click on the PDF and navigate to the download menu.

What’s included in this cheat sheet

The following categories and items have been included in the cheat sheet:

Sniffer Mode

Sniffer Mode
Sniff packets and send to standard output as a dump file
-v (verbose)
Display output on the screen
–e
Display link layer headers
–d
Display packet data payload
–x
Display full packet with headers in HEX format

Packet Logger Mode

Packet Logger Mode
Input output to a log file
-r
Use to read back the log file content using snort
–l (directory name)
Log to a directory as a tcpdump file format
–k (ASCII)
Display output as ASCII format

NIDS Mode


NIDS Mode

Use the specified file as config file and apply 
rules to process captured packets

–c

Define configuration file path

–T 

Use to test the configuration file including rules

Snort rules format

Snort Rules Format
Rule Header + (Rule Options)
Action – Protocol – Source/Destination IP’s – Source/Destination Ports – Direction of the flow
Alert Example
alert udp !10.1.1.0/24 any -> 10.2.0.0/24 any
Actions
alert, log, pass, activate, dynamic, drop, reject, sdrop
Protocols
TCP, UDP, ICMP, IP

Logger mode command line options

Logger Mode command line options
-l logdir
Log packets in tcp dump
-K ASCII
Log in ASCII format

NIDS mode options

NIDS Mode Options
Define a configuration file
-c ( Configuration file name)
Check the rule syntax and format for accuracy
-T –c (Configuration file name )
Alternate alert modes
-A (Mode : Full, Fast, None ,Console)
Alert to syslog
-s
Print alert information
-v
Send SMB alert to PC
-M (PC name or IP address)
ASCII log mode
-K
No logging
-N
Run in Background
-D
Listen to a specific network interface
-i

Snort rule example

Snort Rule Example
log tcp !10.1.1.0/24 any -> 10.1.1.100 (msg: “ftp access”;)

Output Default Directory

Output Default Directory
/var/snort/log
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