There are many different types of computer various, adware, and other malicious software. One that should cause the user some of the most concern is keylogger software, which will secretly keep a log record of the keystrokes made on the user's keyboard. A datalogger will then look through the collected data and look for strings of numbers that seem like credit card numbers or other important or sensitive information.
The reason a keylogger or data loggers can be very dangerous is because if your system becomes infected with one it is very difficult to tell, and the software will do nothing malicious, to avoid alerting the users of it's presence. A well designed datalogger will simply quietly record keystrokes and send them back to a central server. Data loggers, although simplistic, are very cleaver in their design: a user certainly can't avoid using their keyboard - the keyboard is the gateway to any and all important information passing through the computer system.
Think of all the things you do in an average day that could be being watched by data loggers: type in your bank card number for online banking, type in your credit card number for an online purchase, you may even type your social security number for on online application. All of these things could be recorded by the malicious keylogger.
In protecting yourself from malicious software like a keylogger, the most important thing in your arsenal is good antivirus software. There are many, many, different types of software available, and a general rule for most users should be to install both antivirus and antispyware software. The most popular commercial antivirus software is Symantec antivirus, and the most popular free software is AVG antivirus - both are excellent choices. To make doubly sure of your immunity to a keylogger, install an antispyware program as well. A good one is currently offered in the beta stages by microsoft (called, not surprisingly, Microsoft antispyware) - there are also good solutions provided by lavasoft and other companies.
To understand the necessity of protecting yourself from a keylogger, one must understand the concept of identity theft. In recent years identity theft has become increasingly common, particularly in America. Keyloggers, if they catch the right information, can provide malicious users with everything from SIN number to passport ID's to credit numbers. With today's technology, the most difficult part about forging someone's identification is not manufacturing the actual id, it is getting the required information: the numbers and passwords. When a keylogger grabs your credit card number, for example, there is not even any need for the malicious user to manufacture a credit card - they could simply make purchases over the internet with the victim's information (after all - you probably entered your address and other personal information with your credit card number, didn't you?)
By installing antivirus software and using it properly, you can make yourself almost immune to a keylogger, and thus avoid the peril of becoming another statistic in the ever growing world of identity theft.