A computer worm called Prolin is attacking Windows 2000 operating systems, according to a raft of anti-virus vendors including Kaspersky Labs in Russia.Prolin was created by an unknown hacker, using the pseudonym 'The Penguin' which Kasperksy believes identifies the author of the virus as a pro-Linux campaigner. Prolin spreads using a .exe entitled 'creative' masquerading as a Shockwave Flash movie. After the attachment is run, Prolin places itself on to the infected machine's C: directory and starts to search the hard drive for ZIP, MP3 and .JPG files. It then moves these files to the C: directory, adding "Change at least now to Linux" to their filenames. The virus has mainly been found in Poland, but Kasperksy has labelled the worm a medium threat as it can destroy the files it manipulates. Rival anti-virus vendor Network Associates, however, has assessed Prolin as high-risk because the worm has hit at least 50 Fortune 500 companies in the US.