Now if you are looking at a different perspective and are talking about using it as a malicious program then it is a completely different story. There are hackers out there that actually use a keylogger and data logger to get personal information so that they can find out more about the person. When you think about it hackers can use these programs and a lot of other ones to get personal information and you probably would not even know it. Actually some hackers are so good that you would not know it until it was too late.
Key loggers can come in more than one way. The keylogger comes in either hardware or software. There are actually three different types of hardware key loggers. There is the inline device which actually gets attached to the cable of the keyboard. The second one can actually be installed into the keyboard itself and the last is a key logging keyboard. This type of keyboard actually has the key logging hardware installed right inside it. The devices that are attached to the cable are the easiest and fastest to install but it can also be the easiest to detect. As with anything that is being installed, the hardest to install is the hardest to detect and uninstall.
A data logger is pretty much the same aspect. It records anything that is being done at a certain location over a period of time. It can either be a sensor that senses everything or as with a key logger it can be built right into a product. Not only are they small and portable but they are battery operated which makes it harder to trace or detect.
Keylogger and data loggers are basically the same type of software and/or hardware product. Their main purpose is to track/trace what is being done on a computer. The main problem is that there are not a lot of programs or rather anti-viruses that can detect either one. To detect and clean up any key logger in a computer one should try an anti-spy ware program. This seems to work in locating the keylogger on the computer. You should also always keep track what is actually running on the computer. Basically a firewall will not detect the key logger but it will stop the information from being transmitted. The main thing that you need to do is always watch and keep an eye on what you are doing. Keep track of passwords, do not use the same one all the time, change them frequently and always above everything else; always watch your computer and keep track on what is happening with it. If there is anything suspicious takes it some place to have it looked at or if you know someone to help, have them look at it. And mainly, just be plain careful.