At the office, I use Nessus for automated network scanning and patch auditing. With credentials and proper tuning of the scan policy, Nessus is a very powerful tool for more than skript kiddie network scanning. This leaves me with a whole bunch of data to wade through on a weekly basis.
Usually, I only concern myself with the high-severity issues for weekly reports, then as I have time, I dig deeper into the more trivial problems. Still, this required me to manually open the scan files, filter them by severity, and export the data. I got tired of that and made a quick and really dirty XML parser (.nessus files are XML) with shell and grep. It was horrendously slow.
Andy, a fellow KC2600-er helped me wrap my brain around some of the finer points of awk to make it more efficient. This is slightly modified from the one I use at work, which is part of a bigger script that does other things. I figure it's useful for others who use Nessus regularly. The script is here.
Basically, it stores the HostName tag when it encounters it, then iterates through the lines, storing them temporarily until it runs into a line indicating a high-severity plugin has been triggered (severity level 3), then it spits out the host name and the plugin that was triggered. I probably could write the whole thing in awk, but I wrapped it in a little bit of plain old shell script.
Output looks something like this:
Windows
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x.x.x.19:MS10-062: Vulnerability in MPEG-4 Codec Could Allow Remote Code Execution (975558)
x.x.x.19:Adobe Reader <= 9.3.4 / 8.2.4 CoolType.dll SING Font 'uniqueName' Field Parsing Overflow (APSA10-02)
x.x.x.20:MS10-066: Vulnerability in Remote Procedure Call Could Allow Remote Code Execution (982802)
Mac
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x.x.x.8:Mac OS X AFP Shared Folders Unauthenticated Access (Security Update 2010-006) (uncredentialed check)
Linux
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x.x.x.40:PHP 5.2 < 5.2.14 Multiple Vulnerabilities