The latest in a long line of NetSky variants, Netsky-P, tries to lull users into a false sense of security by containing spoofed disclaimers from anti-virus firms.
NetSky-P, first spotted over the weekend, was programmed to begin mass mailing yesterday. After encountering only a few copies of the virus during its "seeding" period, email filtering firm MessageLabs blocked 200,000 copies of the worm yesterday afternoon.
Like previous versions, NetSky-P is a mass-mailing email worm which contains its own SMTP engine. It harvests email addresses from infected machines in order to spread. NetSky-P can also propagate across network shares and P2P networks. NetSky-P - like its siblings - also attempts to remove the Bagle worm from any machine it infects. Subject and body text in infected messages, chosen from a long list, vary substantially.
NetSky-P contains some refinements from earlier variants of the worm. Unlike previous versions it spreads itself inside a dropper. This extracts the main worm's file to a hard drive when it is run, instead of packing its payload into a message attachment, as with previous variants.
The sixteenth incarnation of NetSky also adds fake scan report to the end of an infected message such as:
<type> +++ Attachment: No Virus found
+++ MessageLabs AntiVirus - www.messagelabs.com</type>.
Netsky, Bagle and MyDoom all perform basically similar functions, the most troubling of which is turning compromised machines into zombie clients that can be abused by spammers or other computer criminals. This has led to a theory among anti-spam activists that Netsky, Bagle and MyDoom were all originally developed using the same virus creation tool kit.
However both Alex Shipp of MessageLabs and Mikko Hyppönen of AV firm F-Secure pour cold water on this idea. Each of the viral strains do similar things but the code in each case is different, Shipp told El Reg. ®