Concluding Thoughts

Visual representations of security data quickly convey important information that might otherwise require more time-consuming analysis, and they can be a boon for those of us who need to sift through mountains of data produced by intrusion detection systems and firewalls. It is often possible to arrive at interesting conclusions by extracting fields from security data and graphing those fields with simple criteria such as destination ports over time or outbound connections from local networks. For iptables data,2 psad provides the means to extract the data fields from iptables logs, and the Gnuplot and AfterGlow projects bring the data to life in graphical form.

2 Many administrators have raw packet data in PCAP files collected from various points within a network. Even though psad does not yet interpret PCAP files, you can use a tool like tcpreplay (see to send this packet data against an iptables firewall so that iptables can log the packet data for rendering by psad, Gnuplot, and AfterGlow. This idea was suggested to me in email correspondence with Richard Bejtlich.

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