Bots and Spam
One of the major contributors to spam emails are computers which are called bots (or zombies). Bots are computers which have become infected with one or more programs which allow other people to control what the computer does (e.g. if a bot program is installed on your computer someone else could make your computer send out spam Emails all day long and you may not even notice). Sending spam is only one of a number of bad things that bot controllers can do with your computer, but it is one of the most visible.
Most bot programs are designed so that you won’t notice them because if you noticed something wrong you might investigate and remove them, thus reducing the number of machines at the control of the person who is controlling the computers running that particular bot program. This is why you could have a bot program installed on your computer at this very moment and not know it.
Gone are the days when, if you were infected by a virus, your machine would just crash and you would have to reinstall everything, you are now just as likley (if not more so) to find a virus installs a bot program and then someone else takes control of you machine. This is one good reason to ensure that if you don’t think you have the technical expertise to protect yourself against bots you should install a good Anti-Virus and Anti-Spyware program.
If you want to get an idea of how big the bot problem is have a look at http://www.shadowserver.org/wiki/pmwiki.php?n=Stats.BotCounts it will give you an idea of how many bots there are, and also shows that in general, the number is increasing (and apart from the odd drop when people get new computers which replace old infected ones such as at Christmas time).
So please, please, please, for the sake of everyone who has ever received unwanted emails, perform a spyware and virus scan on your computer. If you can’t afford software to protect yourself you may want to use one of these free products;
Trend Micro Housecall - http://uk.trendmicro-europe.com/consumer/housecall/housecall_launch.php
Spybot Search & Destroy - http://www.spybot.info/
AVG Free - http://free.grisoft.com/doc/1