What Is a Bot (or Zombie)?
A 'bot' is a type of malware which allows an attacker to gain complete control over the affected computer. Computers that are infected with a 'bot' are generally referred to as 'zombies'. There are literally tens of thousands of computers on the Internet which are infected with some type of 'bot' and don't even realize it. Attackers are able to access lists of 'zombie' PC's and activate them to help execute DoS (denial-of-service) attacks against Web sites, host phishing attack Web sites or send out thousands of spam email messages. Should anyone trace the attack back to its source, they will find an unwitting victim rather than the true attacker.
Identifying A 'Zombie' Computer
'Bots' are good at hiding in the shadows of your computer so that they are not noticed. If you could easily detect that something was running on your computer, you would quickly remove or disable it. They often have file and process names that are similar, or even identical, to normal system file names and processes so that users won't think twice even if they do see them.
If you notice anything odd, like your computer seems to slow down or crash for no apparent reason, you might suspect that there is some malware running in the background causing a problem. There are other reasons for symptoms like those as well though. Scan your computer with current versions of anti-virus and anti-spyware software to detect any known malware. If those scans don't find anything, you might refer to a book like Degunking Windows to help you clean the cobwebs out of your PC.
Protecting Your Computer From 'Bots'
One of the best defenses against threats like these is to run anti-virus and anti-spyware software on your computer. It is important that you update the software frequently though. The authors of malware such as 'bots' constantly update and revise their attacks to evade detection and bypass measures like anti-virus and anti-spyware utilities. You should also make sure you keep your operating system and applications patched against known vulnerabilities and use a personal firewall program of some sort to shield your computer from unauthorized access.