SNORT

Tool Description Overview 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

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 Options USAGE: snort [-options] <filter options> snort /SERVICE /INSTALL [-options] <filter options> snort /SERVICE /UNINSTALL snort /SERVICE /SHOW Options: -A Set alert mode: fast, full, console, or none (alert file ale rts 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 can be inconsistent or out of date Since the solution comprises several free tools, each tool may have separate issues

Summary Snort is the Swiss Army Knife of Intrusion Detection Open Source means (hopefully) constant improvements Free tool 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