Spyware is a program that monitors or spies on what computer users do on their computers. They then send the information that is gathered over the internet back to companies. The companies then bombard computers with advertisements.

Adware is a program that monitors or spies on what computer users do on their computers. They then automatically install advertisements onto the computer. ...

A boot sector virus is a computer virus which infects the boot sector on hard disks, floppy disks, and theoretically also other bootable media such as CD's and DVD's.

A boot sector virus does not need to be able to successfully boot the victims computer to infect it. Because of this, even non-bootable media can spread a boot sector virus....

Malware is a generic term for bad software. The word malware comes from the words malicious and software. Malware includes things like spyware or adware programs, such as tracking cookies, which are used to monitor your surfing habits. It also includes more sinister items, such as keyloggers, Trojan horses, worms, and viruses.

Most malware programs will reinstall themselves even after you think they have been removed. They typically hide deep within the Windows registry, making them difficult to manually remove. When this occurs, your computer may become so unstable that installing a malware removal tool may be impossible....

A trojan horse is a malicious program, usually disguised as something useful or desirable. When activated, they can cause loss, damage or even theft of data. Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate.

Trojan horses spread when people are lured into opening a program because they think it comes from a legitimate source. Trojan horses can also be included in software that you download for free. Never download software from a source that you don’t trust....

A wormis a program that is designed to replicate and spread throughout a computer system automatically , it has the capability to travel without any help from a person. It will usually hide within files and distribute those files through any available network connections.

The biggest danger with a worm is its capability to replicate itself on your system, so rather than your computer sending out a single worm, it could send out hundreds or thousands of copies of itself, creating a huge devastating effect. For example, a worm could send out copies of itself to everyone listed in your e-mail address book, and their computers would then do the same, which causes a domino effect of heavy network traffic that can slow down business networks and the Internet as a whole. When new worms are unleashed, they spread very quickly. They clog networks and possibly cause a long wait for you (and everyone else) to view Web pages on the Internet....

All computer viruses need to be run in order to be activated. Once activated, a virus may replicate into only one program at a time, it may infect some randomly-chosen set of programs, or it may infect every program on the system. Sometimes a virus will replicate based on some random event or on the current value of the clock.

In general a virus performs four actions. ...