Distributed denial of service (DDoS) attacks are costing companies an average of $40,000 (£25,400) per hour, with around half of attacks lasting at least six hours and costing $500,000 (£317,570) per event.
These are the findings of a study by cyber crime protection firm Incapsula, which carried out a survey among 270 organisations in the US and Canada.
Fifteen per cent of respondents also revealed costs rising as high as $100,000 per hour in some circumstances.
Incapsula found that in the first half of 2014 there was a 350 per cent increase in large-scale DDoS incidents, and that they lasted longer and proved more powerful than ever before.
The cost of such attacks is calculated not just purely from an event mitigation standpoint, but on the general effect across the whole company too.
“Costs are not limited to the IT group; they also have a large impact on units such as security and risk management, customer service, and sales,” says the report.
“Additionally, most respondents who had been targeted experienced a variety of non-financial costs. Eighty-seven per cent experienced at least one non-financial consequence, such as loss of customer trust or loss of intellectual property,” it continues.
Back in June 2014, Computing reported that DDoS attacks had hit 41 per cent more organisations than in the previous year, with more than three-quarters of those companies targeted twice or more within the same time time period.
However, that research, which was carried out by BT, showed that only 36 per cent of firms in the UK saw DDoS attacks as a key concern for their business.
Major organisations badly affected by DDoS attacks this year have included Sony (more specifically its PlayStation Network service), and multi-platform note-taking app Evernote.