How do I find and remove malicious software from a PC?

Q I received an email from one of my friends that suggested I buy something from a website. I deleted the email, but then heard from other friends saying that they had received similar emails from me.

When I checked my outbox, it contained the sent messages my friends described, though I obviously did not send this to them.

Since then I have had countless emails coming and going from my address without my knowledge, referring people to different websites. Is there a way to stop this spam mail using my contacts and sending mail out silently?

Mike V

A This sounds like a classic case of a malicious software infection, where a hidden program is using your PC and its internet connection to send spam.

If you are lucky, the culprit can be detected and removed using a free tool and we suggest starting with the Trend Micro Housecall online scanner, followed by other malicious software clean-up tools from the same company, each run in turn.

If you’re unlucky, then your PC has been infected by a rootkit and has become a ‘zombie’ that’s at the beck and call of one of the many botnets.

The Trend Micro tools should be able to identify this, but remedying it might not be straightforward and you will need to do more research once the diagnosis is delivered.

Situations like this emphasise the need for keeping Windows fully up to date and using the latest version of whichever web browser you favour – older versions can have security holes that malicious software is able to exploit.

It also underlines the need to have up-to-date anti-virus software installed, since malicious software is less likely to gain a foothold on a PC with it in place.