First published 10 February, 1997 Called Bliss, the virus is important because it is the first to attack Linux, a freeware variant of Unix that is often used in Web site administration. UNIX flavours have always been considered difficult to infect because administration rights are required to create the virus; McAfee believes that multi-user games played in administrator mode may have caused the problem. Bliss manifests itself by overwriting Linux executables with its own code every time it is executed. Files cannot be recovered and files created in other operating systems and stored on Linux servers can also be corrupted. McAfee claims several Bliss infections have been reported and believes the virus originated from a research project. The company has released a version of its VirusScan product for Linux for free download from its Web site.