November 18, 2013 - The UK's National Cyber Crime Unit is warning that tens of millions of PC users across the country are being spammed by e-mails loaded with notorious bitcoin ransomware Cryptolocker.

The NCCU says the mass spamming event appears to be targeting small businesses in particular. It is billing the threat as a 'significant risk'.

The emails - which purport to be from financial institutions - carry an attachment that if downloaded installs the Cryptolocker malware on the user's computer. Cryptolocker works by encrypting the user's files on the infected machine and the local network it is attached to.

Once encrypted, the computer displays a splash screen with a count down timer and a demand for the payment of 2 Bitcoins in ransom for the decryption key. With the price of bitcoins soaring above the $600 mark, the criminal gangs behind the attacks face a bumper payday.

Lee Miles, deputy head of the NCCU says "The NCA are actively pursuing organised crime groups committing this type of crime. We are working in cooperation with industry and international partners to identify and bring to justice those responsible and reduce the risk to the public."