Hijacked Twitter accounts spread Koobface worm
Micro-blogging site suspends compromised accounts
The Koobface worm, which previously infected users of Facebook and MySpace, is spreading among users of micro-blogging website Twitter.
The scale of the attack is unclear but serious enough for Twitter to issue a warning  on Friday morning, via the service's status page. Koobface-related activity has been detected on Twitter before, but the latest assault has provoked a more concerted response from the micro-blogging service, including plans to temporarily suspend compromised accounts.
Some users’ PCs have been infected with a variant of the Koobface malware. This malware sends bogus tweets when the user logs into Twitter.
We are currently suspending all accounts that we detect sending such bogus tweets. If we suspend your account, we will send you an email notifying you of the suspension. This email also includes tips for removing the malware from your PC.
Accounts accessed from compromised PCs inject rogue updates into a Twitter stream, supposedly containing a link to a video but actually pointing towards one of around 20 sites loaded with exploit code that poses as a video codec. Windows users who follow this links and install the "codec" wind up getting infected with Koobface, re-starting the whole infection cycle.
Some messages that point to exploit sites promise "michaeljackson' testament on youtube" while others refer to "My home video :)", Sophos reports , adding that users should avoid following malvertised links.
Panda Security reports  that attempts to install rogue anti-virus (scareware) packages onto compromised machines are made, strongly suggesting that the attack is financially motivated. ®