According to a report whizzing around the net, 40 per cent of spam comes from just one source – which might make you wonder why a few police don't just get in there and unplug the damn machine. But they'd have a job doing so – the source is actually a botnet, a network of tens of thousands of machines whose security has been compromised via dodgy internet sites. This botnet makes the machines' owners – i.e. you and me – unwitting pawns in the spam industry.

Our lackadaisical attitude to online security is the driving force behind this spike, with just six botnets responsible for 80 per cent of all spam. You could conceivably be in the position of actually sending spam to yourself.

The biggest botnet is Srizbi. It runs on your PC without showing any signs that it's at work; it provides the spammer with details of any dead email addresses in its 162 million-strong list; and within the spam messages are links to sites containing more copies of the virus, thus spreading the thing further and wider. All that's required for a torrent of spam to be unleashed is a few mouse clicks at the botnet's HQ.

While Srizbi is obviously malicious in its intent, it doesn't do any noticeable harm to your computer. In fact, its invisibility on each machine is the key to its success – if you knew it was there, you'd obviously try to get rid of it. Protecting against it isn't difficult, as all the main anti-virus programs have been able to detect Srizbi for some months now, but it's nevertheless managed to establish itself on enough unprotected machines to rise to the top of the spamming heap.

So by all means curse the people who wrote Srizbi, but failing to keep your anti-virus software up to date doesn't help the situation. And nor do the men – you know who you are – who keep the industry alive by actually forking out for pills that supposedly add "bonus inches" to their "equipment".

Diagnosis required

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