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Exam Warning There are thousands of worms, viruses, and other malicious software that can infect your computer. Don’t spend significant time memorizing information about them, as in the exam there won’t be questions that target your knowledge about specific viruses and worms. The information provided here allows you to see what viruses, worms, and other malware can do to your system, and how they work. From looking at these worms, we note that it is easy to understand that effective protection against many worms is the timely and prompt installation of patches released by software vendors, especially Microsoft because of its market presence.

Users may unknowingly download them from Web sites or willingly install the spyware believing it to be something else. But more often than not they are tricked into installing it as it is covertly installed as part of another utility’s installation or installed through the exploitation of vulnerability in the user’s browser. As for the method of collecting information, they can record and inform on Web site browsing history, look for information stored in the file system of the computer, or even log keystrokes looking for passwords.

A backdoor is an undocumented and, generally, 8 CHAPTER 1 Systems Security Overview an unauthorized way of gaining remote access to a computer. Once the system is compromised, the backdoor will listen for commands on a network port, allowing the computer to be accessed by a hacker or controlled by the worm’s creator. Exam Warning A worm can take down a system because it has the capability to replicate itself inside of the memory of the target computer. Once it uses up the memory, the system goes down.