According to new research, TorrentLocker, one of the most widespread pieces of ransomware, has claimed thousands of victims since it first surfaced in February 2014.

1.45 per cent, or 570 out of 39,670 infected Windows system, paid the ransom. The pocketed the hackers between $292,700 (£187k) and $585,401 (£375k) in Bitcoins from these payments.

The report indicates that the malware encrypted 280 million documents stored on computers mainly in Europe, but also in Canada, Australia and New Zealand.

The way computers become infected is through an email attachment. It often comes in either a bogus unpaid invoice, package tracking document or unpaid speeding ticket – or follow a link to a site to download the malware. The download web page is mocked up to look like a legit business or government website, such as a national postal service, with a CAPTCHA to look even more genuine.

Tim Erlin, director of security and risk at security tools firm Tripwire, commented: “The absence of the United States on the list of targeted countries is notable, as it’s a target rich environment. It might be that targeting the US results in faster development of countermeasures, or simply that the hit rate on victims actually paying the ransom is lower, or that the US is further down the list and would have been targeted eventually."

Erlin added: ”Spam with malicious links or executables are popular because they continue to succeed,”