Snort & ACID

UTSA IS 6353 Incident Response

SNORT


Overview

• Tool Description• Where You Can Find it• Applicability to Forensics• Tool Use/Screen Views• Observations• Lessons Learned


Technical Description

• What is Snort?– “Snort is an open source network intrusion

detection system, capable of performing real-time traffic analysis and packet logging on IP networks.”

– Performs protocol analysis, content searching/matching

– Can detect all sorts of probes and attacks


Where to Find the Tool

• Snort– www.snort.org

http://www.snort.org/


How Snort Supports Forensics

• Snort is a packet sniffer on steroids.

• Can be placed at different points in a network to provide real time information.

• By logging alerts and rule violations, a systems administrator can be mindful of attacks in progress or research past incidents.


Snort Usage

• Run from the command line or as a Windows Service.

• Lots of options


Snort OptionsUSAGE: snort [-options] <filter options> snort /SERVICE /INSTALL [-options] <filter options> snort /SERVICE /UNINSTALL snort /SERVICE /SHOWOptions: -A Set alert mode: fast, full, console, or none (alert file alerts only) -b Log packets in tcpdump format (much faster!) -c <rules> Use Rules File <rules> -C Print out payloads with character data only (no hex) -d Dump the Application Layer -e Display the second layer header info -E Log alert messages to NT Eventlog. (Win32 only) -f Turn off fflush() calls after binary log writes -F <bpf> Read BPF filters from file <bpf> -h <hn> Home network = <hn> -i <if> Listen on interface <if> -I Add Interface name to alert output -k <mode> Checksum mode (all,noip,notcp,noudp,noicmp,none) -l <ld> Log to directory <ld>•


More Snort Options-L <file> Log to this tcpdump file -n <cnt> Exit after receiving <cnt> packets -N Turn off logging (alerts still work) -o Change the rule testing order to Pass|Alert|Log -O Obfuscate the logged IP addresses -p Disable promiscuous mode sniffing -P <snap> Set explicit snaplen of packet (default: 1514) -q Quiet. Don't show banner and status report -r <tf> Read and process tcpdump file <tf> -R <id> Include 'id' in snort_intf<id>.pid file name -s Log alert messages to syslog -S <n=v> Set rules file variable n equal to value v -T Test and report on the current Snort configuration -U Use UTC for timestamps -v Be verbose -V Show version number -W Lists available interfaces. (Win32 only) -w Dump 802.11 management and control frames -X Dump the raw packet data starting at the link layer -y Include year in timestamp in the alert and log files -z Set assurance mode, match on established sesions (for TCP) -? Show this information<Filter Options> are standard BPF options, as seen in TCPDump


Snort in Action


Snort Raw Output


Snort Logs – Better Information


Observations of Snort - Good

• FREE!

• Large user base

• Community provides constant rule updates

• Free tools to provide log analysis and email/pager alerts


Observations of Snort - Bad

• UNIX tool ported to Windows; behaves like a UNIX tool– Difficult to configure

• Cryptic command line driven interface

• All configuration is driven by files

• Lacks standardized support


Lessons Learned - Snort

• You get what you pay for!

• Documentation for running Snort on XP is inconsistent and out of date.

• Since the solution comprises several free tools, each tool has separate issues with XP.


ACID


Overview

• Tool Description• Where You Can Find it• Applicability to Forensics• Tool Use/Screen Views• Observations• Lessons Learned


Technical Description

• What is ACID?– The Analysis Console for Intrusion Databases

(ACID)– PHP-based analysis engine to search and

process a database of security events generated by various IDSes, firewalls, and network monitoring tools.


Where to Find the Tool

• ACID– http://acidlab.sourceforge.net/


How ACID Supports Forensics

• ACID helps to make sense of Snort data in a visual manner.

• Can help analyze trends and help filter out the noise by categorizing attacks and IP addresses.

• Query-builder and search interface.

• Can provide alerts when events occur.


ACID Usage

• Acid runs as a set of PHP web pages under IIS or Apache.

• Reports, alerts, and information is accessed through the web interface


ACID at Work


Alert Screen


Alert Screen - Detail


Alert Screen – Graph


Observations of ACID - Good

• FREE!

• Nice graphical interface written in PHP, therefore user community to rely on.

• Free tools to provide log analysis and email/pager alerts.

• Helps sort through all the info from Snort.


Observations of ACID - ACID

• Lacks standardized support

• Lots of options to become familiar with


Lessons Learned – ACID

• You get what you pay for!• Configuration is file driven, no GUI.• Most documentation for running ACID

pertains to Apache servers and took some searching to run on IIS.

• Reliance on PHP means that any interesting aspects on running PHP on Windows had to be sorted through.


Summary

• Both Snort and ACID are excellent tools for Intrusion Detection.

• Open Source means (hopefully) constant improvements• Free tools for companies that cannot afford tools or

services provided by other companies.• Can be time frustrating to deal with and requires an

administrator with the time and expertise to master all the options and create a working system.

Snort & ACID

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