You can find all sorts of interesting things on the internet. Such as the fact 30 to 40 per cent of internet use in the workplace is not related to business.

According to the same site (which is trying to sell monitoring software), more than one in four US companies say they've fired employees for misuse of office email or internet connections, and two-thirds report some disciplinary measure for those offences.

More than three-quarters of major US companies keep tabs on employees by checking their email, internet, phone calls, computer files, or videotaping them at work.

A few years ago, the New Zealand police investigated internet and email abuse on its networks, and ended up disciplining 330 employees.

It's an area of evolving law, but there are basic things that can be done to stop small problems escalating.

Automobile Association chief information officer Doug Wilson says everyone needs to understand that anything done on a network can be traced if it needs to be; things such emails and internet logs are backed up and kept. Larger organisations will subscribe to blacklists so they can block websites known to distribute malicious software. "We won't allow people to download music, but we find social media a reality now for businesses," Wilson says.

David Foley, the learning manager at the Northern Employers and Manufacturers Association, says organisations need to set clear guidelines. "We've got over the porn emails, people know the rules, and we're extending that to social media, so there is no difference between putting inappropriate things in an email and putting them on Twitter or Facebook."

That could be trade secrets, or abusing a current or former employer.

David Lowe, the EMA's employment services manager, says the sites most often blocked by employers, because of drain they represent on employee time as much as anything, are the Facebook/Myspace/Bebo type, YouTube and Trade Me.

"It comes down to the amount of time people spend on personal emails and on websites unrelated to their job. There are some jobs where those social networking sites are relevant to what you do, so it's about making sure people can get on and do their jobs," Lowe says.

"It's pretty easy for employers to get a report about how much time is spent online, and usually a gentle discussion is all that is required."

A more serious issue emerging is the online slag-off. Lowe says: "We are seeing it happen more and more. As social networking sites get picked up as business tools, employers are becoming more aware about what is said about them online."

Tim Clarke, a senior associate on Bell Gully's employment law team, says while employers have always monitored staff, new technologies make surveillance even more ubiquitous, especially around emails and internet use.

"A lot of the law round this is still undecided in the New Zealand courts, but there is a tension between and employers' rights to protect confidential trade secrets and an employee's rights to privacy," Clarke says.

"They have protections and rights under the Privacy Act." He says on balance the courts have favoured the ability of firms to surveil employees' activities in cyberspace.

"The employer's argument is often 'you work for me, the computer is provided for work purposes'. Employees see things differently, that some casual use for private purposes is justified.

"That's why it's important to set a policy so you clarify the parties' expectations.