Nearly two thirds of companies have detected attempts to break into their networks in the past year, double that of two years ago, according to the latest biennial Information Security Breaches Survey from PricewaterhouseCoopers (PwC).
The latest figures from the report, which will be launched in full at the Infosecurity Europe show next week, blame the rise in part on the increasing use of cloud computing and social networks within the enterprise.
Around 15 per cent of large organisations said that they had been infiltrated by an "unauthorised outsider" in the past year, and a quarter had suffered a denial-of-service attack, more than double the proportion in 2008, according to the report.
Over three-quarters of those polled were using software-as-a-service and cloud computing, while 44 per cent entrusted critical services to third parties.
Chris Potter, a partner at PwC, described it as worrying that only 17 per cent of companies that allow external providers to handle highly confidential data ensure that it is encrypted.
"Virtualisation and cloud computing seem set to follow the trend established over the last decade of controls lagging behind adoption of new technologies," he said.
"Given the increased criticality and confidentiality of information held in virtual storage, organisations need to respond quickly to close this control gap."
The increasing use of third parties and externally provided services in the current business environment means that organisations are being forced to look to standards to provide some sort of assurances over data protection and compliance, said the report.
Compliance with ISO 27001 is required by 40 per cent of large organisations, for example.
Finally, companies are looking to reverse the policy of relaxing web use restrictions, as data leakage risks on social networking and other sites become more apparent.
Nearly half of large organisations now restrict which staff can access the internet, while less than a third did so in 2008.