Iptables provides the option to log both IP and TCP headers in a log file. This is useful to:
=> Detect Attacks
=> Analyze IP / TCP Headers
=> Troubleshoot Problems
=> Intrusion Detection
=> Iptables Log Analysis
=> Use 3rd party application such as PSAD (a tool to detect port scans and other suspicious traffic)
=> Use as education tool to understand TCP / IP header formats etc.
How do I turn on Logging IP Packet Header Options?
Add the following command to your iptables script beo:
iptables -A INPUT -j LOG --log-ip-options iptables -A INPUT -j DROP
How do I turn on Logging TCP Packet Header Options?
Add the following command to your iptables script:
iptables -A INPUT -j LOG --log-tcp-options iptables -A INPUT -j DROP
You may need to add additional filtering criteria such as source and destination ports/IP-address and other connection tracking features. To see IP / TCP header use tail -f or grep command:
# tail -f /var/log/messages
Recommended readings:
- TCP Protocol
- iptables man page
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