Julie Amero is a teacher from Windham, a small town in Connecticut, USA. In October 2004 her class room computer started showing pop-up pornographic images. Despite the computer almost certainly being infected with spyware, the school not having up to date anti-virus programs and internet filtering, Mrs Amero was convicted last month of "impairing the morals of a child".

She faces up to 40 years imprisonment.

This case is an extreme example of the risks involved in spyware. We’ve seen innocent people being accused of visiting inappropriate sites even when all they’ve done has looked for music lyrics. In some cases this has cost people jobs and relationships.

Could it happen in Australia?

In theory, yes. All states have similar child endangerment laws like Connecticut’s. Hopefully our police, prosecutors, judges and juries wouldn’t draw as long a bow as those in the Amero case have.

For businesses, the situation is different. Business owners are responsible for inappropriate material in the workplace. In this respect, pornography on a computer is little different to a girly calendar on the tea room wall, it’s not acceptable.

The biggest problem is where workers share computers. We’ve seen situations like doctor’s surgeries where one doctor has surfed to inappropriate sites. Other doctor using that computer later have complained about the rubbish on the computers.

Bizzarely most businesses don’t want to deal with the problem. They figure the cost of filtering and developing procedures is too high. This is a gamble as a  sexual harassment case could turn out to be extremely expensive.

How does this stuff get onto your computer?

Almost everything your look at on the web is saved on your computer in one way or another. This is to help your browser start faster should you re-visit a page. Sites you visit are logged on the machine and often by your office or ISP system administrator.

The problem is that it isn’t just the sites you want to look at that are saved. Every advert and every pop-up is also recorded. This is where people can be accused of downloading inappropriate material.

How to protect yourself

Our security kit is the first step. Locking down the computer will help protect from viruses and spyware but not from inappropriate websites. Even if you don’t intend to visit sites that attract this sort of thing, a mis-spelling or a spam email can still leave this information on your computer.

For households, an important step is Internet filtering. The Federal government’s NetAlert program has a list of suitable filters. Filtering is not the complete answer as they can be beaten and require updating to keep track of new sites.

Internet filtering for businesses is a much bigger task. The best way of protecting a network is by using a firewall appliance. A five person business can expect to pay around $2,000 for the appliance and another $500 a year for updates.

Filtering is not infallible as users can skirt around it and the filters need to be constantly updated. So there needs to be some supervision on computer use. Business should also make sure they have enforceable usage policies that clearly explain what is not acceptable and what the consequences are.

The Julie Amero case is a tragedy which we hope will be fixed on appeal. But the lessons are clear for computer users you need to be careful with what is on your computers. The stakes can be very high.