A worm which tries to disguise itself as a security patch is hitting Asia particularly hard.
Fbound normally arrives as an email with the subject line 'Important' and has an attached file called 'Patch.exe'. Once activated, the worm forwards itself to everyone in the victim's email address book using its own SMTP routines.
When sending itself to an email address ending in .jp, the worm uses one of sixteen different subject lines - written in Japanese characters, in a deliberate attempt to fox Asian as well as English speaking users. The worm doesn't harbour a particularly dangerous payload, though it could affect the speed of Internet connections.
MessageLabs, a managed services firm which scans its users' email for viruses, reports blocking 4,943 copies of the worm since it first appeared yesterday. It's become the most common piece of malware on the Internet though its spread is far short of that of other recent outbreaks, such as the Goner or the infamous Anna Kournikova worm.
Fbound's main trick of pretending to be a security patch is a well known virus writer ploy, most recently seen in the Gibe worm, which poses as a patch for a MIME header vulnerability in Internet Explorer. Half a dozen of you have contacted us about this virus over the last week, so it's obviously doing the rounds.
Credit Microsoft with enough sense never to send out its security patches by email. Messages along these lines should simply be deleted.
Antivirus vendors have updated their software to detect both Gibe and Fbound, both of which only affect Windows machines, so now might be a good time to update your protection.