Most websites are safe to use, but some can cause damage to your PC, or even be used to defraud you. There are several tools available that purport to be able to tell you whether or not a site is safe to visit. We will find out how well they work and where they fall down.

The tools to protect against unsafe sites range from those built into web browsers and search engines to add-ons and toolbars that you can download and use to check suspect sites.

However, the efficiency rate of each method varies – some are more prone to ‘false positives’ where a site is marked as bad when it isn’t. On the other hand, some methods are more prone to letting bad sites slip through.

What is a malicious site?
Malicious websites can work in many ways. Some are basic phishing sites, which are designed to look like the entrance page to online banking sites, Paypal or Ebay, among others. They encourage visitors to enter usernames, passwords and other information, and then use that information to defraud them.

Then there are the sites that deliver malicious software such as viruses or spyware to your computer. You may not need to click anything on the website; sometimes visiting it is enough to infect your computer. Other sites might contain content such as copyrighted music downloads or illegal pornography. Less seriously, a site may be known for sending out spam.

The tools listed below can generally be used together – in most cases they check different things in different ways. They should always be used in conjunction with your internet security software (anti-virus, anti-spyware and firewall programs), which should be fully updated at all times. Site-checking tools may even be included with your internet security software.

Basic protection
The most basic site-checking tools are built into your browser. The main browsers include anti-phishing protection. Each site you visit is compared against a list of known bad sites. If the browser detects that you’re trying to visit one of these, it will display a warning message and ask you if you want to continue.

These filters can be turned off, but if you leave them on, details of each site you visit will be sent over the internet to be checked – this data is anonymous. Sites listed tend to be phishing sites rather than those that cause any other kind of problem.

This form of blocking is harder to get around, so the sites that are listed have normally been confirmed as being bad. Some sites slip through the net, though.

The next line of defence is built into search engines. If you use Google you may see the words ‘this site may harm your computer’ under certain search results. This means the site has been marked by Google as being potentially bad and likely to infect your computer.