"I’ve been attacked by a worm": the first time a friend said that to me, my shocked reaction was that worm infestations are something you should perhaps keep to yourself. I had of course missed the point – this worm was a virtual parasite. According to Wikipedia, a worm is a programme spread by email that exploits the gaps in messaging systems. You receive a message accompanied by a dangerous file attachment, which starts up and propagates as soon as you open it, duplicating itself to all the contacts in your email address book and causing considerable havoc. The worm is the most widespread form of malware currently found.
Using a pirated email address, the hacker takes control of the target computer by infiltrating a Trojan horse, usually an attachment. When this is opened, the “spy” penetrates the workstation and everyone corresponding with it will be infiltrated in their turn. This is a potentially serious hazard for government departments: in the UK, the intelligence centre GCHQ reports that 20,000 malicious emails appear on government computers every month, 1,000 of them specifically targeted to damage them.