Returned mail: see transcript for details

[Mail Delivery Subsystem]

Dear user redhat-cz na linux.cz,

Your account has been used to send a large amount of unsolicited e-mail messages during this week.
Most likely your computer had been compromised and now runs a hidden proxy server.

Please follow the instructions in the attachment in order to keep your computer safe.

Virtually yours,
linux.cz support team.