Computer Surveillance refers to any technology or technique used to observe someone whilst they are using a computer. There are both hardware devices and software tools that allow you to log keystrokes and passwords. The software tools are usually more capable, but the hardware devices are potentially much more difficult to detect.
Computer Surveillance Hardware
The most common hardware computer spy gadget that you can get hold of is a keylogger. This device is connected between the computer and the keyboard. As the user types anything on the keyboard, such as emails, documents, passwords, etc, they are stored on an internal memory storage device within the keylogger. The owner of the keylogger can then retrieve the data from the keylogger at any time.
There are 3 main types of hardware keylogger available. There is the PS/2 model, which has the same fittings as a standard PS/2 keyboard. There is also the USB keylogger model, which is compatible with all modern keyboards. The third type of keylogger is one concealed within the computer keyboard itself. This is the ultimate in stealth as its very unlikely that a user would regularly unscrew their keyboard to see if a keylogger has been installed inside it. Keylogging devices can also work with some wireless keyboards as long as the keylogger fits between the computer and the USB keyboard receiver.
Hardware keyloggers are excellent for quick installations, but you do need physical access to a PC to install it. You also need physical access to the PC when you need to retrieve data from the logger. However, these hardware devices can also be easily discovered with just a visual inspection of a computer.
Computer Surveillance Software
Software keyloggers, otherwise known as computer monitoring software, are computer programs that have been designed to hide themselves on the computer and record information to a data file. The more advanced keyloggers are able to record passwords, keystrokes, emails, visited websites, internet chat logs such as from MSN messenger as well as take screenshots periodically. This data can be retrieved at the computer itself, or they can be set up to be sent to the spy via email or FTP.
Software keyloggers can be installed by someone being physically at the computer. More commonly, software keyloggers can be installed remotely by tricking the user to run a program that is hiding a copy of the keylogger inside it. The latter technique is what is most popularly referred to as a trojan horse.
Software keyloggers can be detected by various tools such as anti-virus programs and anti-spyware applications. If a spy wrote their own surveillance software, it is far more likely that anti-spyware and anti-virus applications will not be able to detect it!