Two out of every three visits to pornographic web sites occurs during working hours, according to new European research.
A survey by web security company Panda GateDefender Performa suggested that personal use of the internet while at work is estimated to account for almost an hour of employees' time every day.
Meanwhile, Panda claimed, the average annual cost of computer attacks for a company with just 10 employees but without adequate security devices had soared to €136,000.
This figures takes into account loss of productivity, use of bandwidth consumption and the amount of time dedicated by IT staff to cleaning up the network.
Spam is another major time-water, making up an estimated 21 per cent of email reaching companies, Panda said. Some five per cent of all traffic is also infected by some type of malware.
In addition, almost 40 per cent of internet use in companies was non-work related – with most visits to pornographic web pages occuring during working hours.
Alongside personal use of the internet, companies are becoming increasing concerned about the security of new technology, with managers worried about the ease with which confidential material can be downloaded on iPods or memory sticks.
There are also concerns that employees often fail to be security conscious enough when travelling on business, particularly on trains.
A separate poll has revealed that almost a third of British directors have stolen confidential information from their employers.
About 29 per cent of the 1,385 employees surveyed by IT company Hummingbird admitted to taking confidential company material when they left for a new job.
Company training manuals and procedure handbooks were found to be the most popular items, followed by financial data and client reports.
Women were found to be less likely to thieve than their male colleagues, however.
More than a third said they would never pinch unauthorised information compared with just a quarter of men.