An NCA spokesman commented: “The emails may be sent out to tens of millions of UK customers, but they appear to be targeting small and medium businesses in particular. The emails carry an attachment that appears to be correspondence linked to the email message, for example, a voicemail, fax, details of a suspicious transaction or invoices for payment.”
"This file is in fact a malware that can install Cryptolocker - which is a piece of ransomware. Cryptolocker works by encrypting the user's files on the infected machine and the local network it is attached to. Once encrypted, the computer will display a splash screen with a countdown timer and a demand for the payment of 2 Bit coins in ransom for the decryption key."
The spokesman added: "The NCA would never endorse the payment of a ransom to criminals and there is no guarantee that they would honour the payments in any event."