Yet another NetSky virus arrived on the scene today. NetSky-V spreads using a well known Internet Explorer vulnerability, connected with the handling of XML pages. Instead of depending on users double clicking on infectious email attachments, the worm can spread automatically across vulnerable Windows boxes.
Users can be infected by NetSky-V simply by reading an infected email.
Just as well then that NetSky-V, although it has been observed in the wild, is far less common than previous versions. Most anti-virus firms rate NetSky-V as low-to-medium risk. A previous variant, NetSky-Q ,was also capable of auto-execution but it used a different exploit mechanism (an IE iFrame vulnerability, dating back three years) to the vulnerability exploited by Netsky-V.
Emails contaminated by NetSky-V come with subject lines such as 'Converting message. Please wait...' and exploit code which attempts to download a copy of the worm from an infected user's computer.
The worm's payload contains code designed to spread infectious emails to addresses harvested from victim machines, which become zombie drones.
From 22 to 29 April, NetSky-V is programmed to launch a denial of service attack on file-sharing and warez websites (www.cracks.am, www.emule.de, www.kazaa.com, www.freemule.net and www.keygen.us).
Four previous versions of NetSky have targeted a similar list of sites. NetSky-Q infected more machines than its DDoS worm siblings and was therefore responsible for the most severe attack to date.
Sites such as www.kazaa.com remained up and running during an attack by NetSky-Q between 8 April and 11 April. However www.cracks.am was seriously bogged down. Other sites targeted by Netsky-Q - www.edonkey2000.com and www.emule-project.net - removed themselves from DNS records during the duration of the attack.
Mikko Hyppönen, director of nti-Vivrus Research at Finnish AV firm F-Secure, said the attacks "were fairly successful since most of the sites, except Kazaa, went down."
Advice to defend against Netsky in all its varied guises follows a familiar pattern: update AV signature files, apply patches, use a personal firewall and wear a regulation tin-foil hat. ®