Attacking Nimda-infected attackers
A presentation at Blackhat last week by Tim Mullen of AnchorIs, offering a novel treatment for the Nimda worm, has caused considerable controversy because it involves taking unauthorized actions against the offending box.
Mullen has come up with two possible ways of shutting down the bandwidth-hungry attacks when an infected IIS box attempts to spread the worm, each with its own advantages and problems. Method one places a bit of harmless code in the boot sequence which simply precludes Nimda from loading. The advantage here is that the machine will be made harmless without interfering with any functionality or damaging any files. The disadvantage is that it involves privilege escalation and requires a remote re-boot, which are a bit aggressive however therapeutic they may be. The sudden re-boot could also be problematic where cached writes are common and RAM drives are in use, though supposedly Windows will handle them gracefully as it shuts down.
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