Two Polish men were arrested at Heathrow Airport earlier this week in connection with an alleged DDoS extortion attack on a Manchester-based business, news sources have reported.

Details are light but it is known that a website connected to the business was brought down during the attack, which happened at an unspecified time before the 7 August arrests.

"This investigation centres on an allegation that the on-line company was blackmailed,” said Detective Inspector Chris Mossop, of Greater Manchester Police’s Serious Crime Division

"As part of this blackmail attempt, one of the company's websites was made temporarily unavailable by the offenders,” he added.

"Denial of service attacks have become increasingly common offences in recent years and can have a devastating effect on the victim's on-line business or presence.”

The investigation continued in several countries, including the UK, the US and Poland, police said.

Although such cases rarely come to light, cyber-extortion has flourished in the last decade. In almost every case, DDoS is the weapon of choice.  These days, small and medium-size businesses are the usual target because they are far less likely to have DDoS mitigation in place to defend themselves.

The other less common technique involves attackers stealing data and threatening to release it unless a ransom is paid. An example of this type of attack came to light last year when a Belgian bank was blackmailed by hackers.

Last December, hackers tried to extort $4,000 AUS (£2,600) from a medical centre in Australia after breaching its network and encrypting its customer database.

A recent survey suggested that one in five UK businesses had been affected by DDoS attacks during 2012.