The popularity of singer Avril Lavigne has spread to the world of computer viruses.

Lirva (w32.Lirva@mm), also known as Naith, is a mass-mailing worm that is UPX-compressed to a file size of 32,766 and arrives via e-mail either announcing a new Microsoft patch or offering fan access to Avril Lavigne. Once active, Lirva will attempt to e-mail copies of itself to all contacts on an infected system, shut down all antivirus and firewall programs, and launch a Web browser to open the Avril Lavigne Web site on an infected user's desktop.

Lirva uses the Iframe vulnerability, so on unpatched systems, the worm will automatically execute whether or not the attached file is opened. Antivirus vendor MessageLabs reports that parts of the Lirva worm code very look familiar, so Lirva may turn out to be a variant of a known virus family.

Lirva arrives as e-mail with one of several subject lines including: Fw: Prohibited customers...; Re: Brigade Ocho Free membership; Re: According to Daos Summit and Fw: Avril Lavigne - the best.

The e-mail containing Lirva may also include the following information in the body text:

Patch is also provided to subscribed list of Microsoft® Tech Support: to apply the patch immediately. Microsoft strongly urges all customers using IIS 4.0 and 5.0 who have not already done so and do not need to take additional action. Customers who have applied that patch are already protected against the vulnerability that is eliminated by a previously-released patch. Microsoft has identified a security vulnerability in Microsoft® IIS 4.0 and 5.0 To prevent from the further buffer overflow attacks apply the MSO-patch Attachment you sent to %s is intended to overwrite start address at 0000:HH4F Restricted area response team (RART) Admission form attached below Vote for Im with you! FanList admits you to take in Avril Lavigne 2003 Billboard awards ceremony Avril fans subscription

The attached file may have the name IAmWiThYoU.exe.

Once active, Lirva will attempt to shut down all security programs such as antivirus and firewall software. It will search an infected hard drive for all HTML files in an attempt to locate e-mail addresses, then use its own SMTP engine to send copies of itself to those addresses. Unlike several recent viruses, such as Sircam, Lirva does not appear to spoof the sender's address.

Lirva will also open a browser and display an Avril Lavigne Web site. MessageLabs points out that this may have the unintended effect of creating a denial-of-service attack if several thousand infected PCs all try to access the site at once.

Initial analysis suggests Lirva may also spread via IRC.

Users of Microsoft Outlook 2002 and users of Outlook 2000 who have installed the Security Update and have installed the patch for the MS01-020 vulnerability in Internet Explorer should be safe from Lirva. Users who have not upgraded to Outlook 2002 or who have not installed the patch for the MS01-020 vulnerability should do so. In general, do not open attached files in e-mail without first saving them to hard disk and scanning them with updated antivirus software. Contact your antivirus vendor to obtain the most current antivirus signature files that include MyLife.

A few antivirus software companies have updated their signature files to include this worm. This will stop the infection upon contact and in some cases will remove an active infection from your system. For more information, see Central Command, McAfee, Sophos, and Trend Micro.

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