New variants of the prolific Bagle worm were spreading across cyberspace Thursday morning, prompting several antivirus firms to issue alerts.
Bagle-AY and Bagle-AX spread through tainted e-mail messages. Kaspersky Lab of Russia issued a severe-risk alert to its customers, while Danish security firm Secunia labeled the worms a medium-risk.
At this point, Bagle-AY appears to be spreading more rapidly. In addition to e-mail, Lynnfield, Mass.-based antivirus firm Sophos said this variant also spreads through peer-to-peer file-sharing networks. And it will try to disable antivirus and other security tools running on infected PCs.
"Everyone should be cautious of unsolicited e-mail attachments and be wary of what they download from Internet file-sharing networks," Graham Cluley, senior technology consultant for Sophos, said in a statement. "So far, 2005 has been fairly quiet in terms of brand new virus outbreaks. If everyone applied computer security common sense it would help keep it that way."
According to Sophos, the worm uses such subject lines as:
- Delivery service mail;
- Delivery by mail;
- Registration is accepted;
- Is delivered mail; and
- You are made active.
Finnish security firm F-Secure said Bagle-AY sightings had been reported in several different countries by early Thursday morning. The firm said this variant was similar to Bagle-AX in that it is polymorphic, arrives in e-mails with variable subjects and attachments and has peer-to-peer spreading capabilities. Bagle-AY also contains a backdoor that listens on TCP port 81 and is programmed to cease its activity on April 25, 2006.
Secunia's advisory links to alerts from seven antivirus firms and includes different aliases each use to identify the new variants.