A new worm, similar to Yaha, has been discovered in the wild, mainly in the UK and The Netherlands.
'SoBig-A' affects PCs running Windows 95 onwards. It contains an SMTP engine to mail itself out to all addresses on the PC, and can spread through network shares.
The worm is easy to spot, with just four subject headers and attached file names.
These are: 'Re: Movies', 'Re: Sample', 'Re: Document' and 'Re: Here is that sample'.
The infected attachments are: 'Document003.pif', 'Sample.pif', 'Untitled1.pif' and 'Movie_0074.pif'.
Carole Theriault, antivirus specialist at Sophos, said: "We're not getting a lot of new reports as companies have got patches in fast. Basically, if you block .pif files anyway you won't be troubled by this one."
The worm also attempts to download and run software from an external website.
All antivirus software vendors have a patch available.
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