When a little bit of that signature changes, does the anti-virus scan pick it up or not?

FORBES: Crimes No One Can Stop -- Attackers No One Can Find

Remember that no legitimate anti-virus company will perform an unsolicited scan of your computer and ask for payment to correct issues identified.

FORBES: The Proliferation Of Scareware Hits Home

"We are in the process of notifying impacted users and recommending that they scan their computers and run current anti-virus tools--good advice for all internet users, " they added.

BBC: NEWS | Technology | Bloggers battered by viral storm