Abuse of the internet is now a major headache for UK employers, according to a new study on the growing problem.
Internet abuse is a growing problem for employers
The survey found that almost a third of companies had dealt with up to five disciplinary cases in the last year.
A further 5% of the firms questioned by human resources guide LexisNexis Industrial Relations Services reported more than six incidents.
Disciplinary action is now common for infractions, which range from sending rude emails to viewing pornography.
The new survey follows after a number of recent high profile cases of internet misuse.
Back in September 2000, mobile phone network Orange admitted it had sacked 40 members of staff for the "distribution of inappropriate material".
Employers were also sacked or disciplined at insurance company Royal and SunAlliance, and bank Merrill Lynch, following the distribution of pornographic images and emails.
Mark Crail, managing editor of LexisNexis IRS's Employment Review publication, said the issue was a continuing headache.
"Employers are just getting to grips with it now, and many employees are not taking it seriously enough," he said.
"Companies can block access to inappropriate web sites using sophisticated screening software, but many try to address this issue through employment policies instead."
Mr Crail said that in addition to blocking access to certain websites, employers could insist their staff adapt the same level of formality in external emails as they would use in a writing a letter.
However, new laws addressing the computer rights of workers have added to the problem for companies, added Mr Crail.
He said the recent legislation has forced firms to strenthen their codes of conduct to make exactly clear which internet and email activies are off-limits.
More and more firms are also introducing email filtering software, which can block messages that contain inappropriate words or images.
Alyn Hockey, director of research at Reading-based Clearswift, one such company which offers email filtering systems, said: "Security is not just about protecting yourself from spam and viruses, as employees are often the weakest link."
The LexisNexis survey spoke to 63 UK firms with a total of 97,000 employees.