The spy inside your home computer

Beware: Pretty programs can hide unwanted guests

By Mark Ward BBC News Online technology correspondent

Bond may be back, but spying never went away. The worrying truth is that secret agents could be lurking in your home computer and broadcasting personal information.

Your home computer is a pretty dumb device that usually does what it is told. But with the right help this mute machine can become disturbingly "talkative".

So-called "parasite programs" are logging what you do online and, like a nest of busy gossips, sharing the information with anyone who will pay to listen.

Not all spies are so obvious

As concern mounts over these sneaky tactics, privacy experts, cyber watchdogs and many concerned net users have started to compile lists of these programs.

Most parasite programs divide into two categories:

• "adware" - programs on your computer that fling pop-up ads at you, install toolbars full of adverts or hijack searches and web use; and

• "spyware" - more underhand, these devices surreptitiously watch what you do, steal personal information and despatch it across the web.

What they have in common, is that they quietly download onto your computer while you are online.

Assume everyone is out to get you

Andrew Clover

Sometimes they come attached to software you download from the web - the details are often included in the license agreement small print that most users click through without reading.

And sometimes they don't even need your permission to download, but just hop on your hard drive, totally unannounced, because you are browsing the wrong webpage.

Innocuous uses

Many people first notice something is up when they install a firewall, such as ZoneAlarm, which only lets programs with explicit permission access the net.

Think twice before downloading programs

"You still have to be careful of things bundled with downloads," Andrew Clover, who runs a site that tests your computer for installed spy- and adware, "but there has been a boom in software automatically installed by web pages recently."

There are many innocuous uses for these programs, common to nearly all the world's biggest websites, including the BBC, which merely log how long the page took to load and how long someone had it open.

But it's the other uses and the fact this information can be sold to third parties, which are worrying privacy campaigners.

Test your computer

Sites detailing common adware and spyware programs and the places they hide and what they install, abound on the web.

As with anything, read the small print

Many, like Mr Clover's, will test your computer for spyware and give advice on how to remove them and reclaim your computer for yourself.

But the adware supporters are hitting back. Some programs, such as Radlight's DivX movie player, actually un-install anti-adware devices.

Some , such as EZula, impose their own links on the pages you are looking at to ensure you stick with their sponsors.

Others, such as Anti-Leech, help ensure only those who see the adverts go on to see the website.

'Avoid Explorer'

A few companies are now exploiting holes in Windows messenger to sneak adverts on to the screens of unsuspecting users.

Some firms are blocking adware blockers

"The only simple advice I can think of is: 'assume everyone is out to get you!'" says Mr Clover.

The easiest way to avoid parasite programs, he says, is to stop using Internet Explorer because it is targeted by many of the adware and spyware companies.

At the very least, people should ensure they have installed the latest security patches, says Mr Clover.

"Never, ever click 'Yes' to a 'Do you want to download and install?' prompt unless you 100% sure the people who made it are trustworthy," he warns.

Loopholes

Fears about adware and spyware are not just for privacy fetishists and cyber-libertarians.

Much of this surreptitious software is badly written and can crash your computer, others simply slow down your machine and make web use a chore.

But the real danger is the fact that many of the loopholes in Windows that these programs exploit are being increasingly used by virus writers.

If you do nothing to close these holes then one day you may lose much more than information about your online habits.