Dangerous worm Gruel spreads by e-mail in messages with infected executable attachments. Usually these messages contain fake information from well-known software developers, such as Microsoft or Symantec. The worm uses it to trick a user so he or she could run an executable attachment. After such attachment was executed the worm starts its process, which deletes lots of critical system files, sends copies of the worm to other addresses and shows fake Windows error messages. The Gruel also can disable some system functions and hang the infected computer. There is a very high possibility that the infected computer will fail on next startup, because its operating system may get totally corrupted.