Antivirus makers have warned of new variants of the Bagle worm spreading in Asia and Europe networks since Friday morning. According to reports, the newer variants are not destroying files or damaging software, causing little apparent damage to users other than filling up mail accounts rather quickly because of the executable viruses that come attached to the messages.

McAfee has rated the new and variants as "medium" threats, based on the number of submissions they received for each.

Like the first worm, all subsequent versions target systems running Windows, harvest e-mail addresses from infected machines, and use their own Simple Mail Transfer Protocol to send virus-infected e-mail to addresses it captures. Bagle can also spread over peer-to-peer networks, planting files disguised to look like pornography or software in shared folders used by the networks, he said.

The new Bagle variants arrive in e-mail messages with forged or "spoofed" source addresses and vague subjects such as "Re:Hello," "Re: Thank you!" and "Re: Hi," according to McAfee.