Nightmare edition

Got all of these by experiences.

Worms — A worm is similar to a program but doesn't need to attach itself to another program to run. Trojans — A Trojan poses as a legitimate program but is designed to disrupt computing on the PC it infects. It is not designed to spread to other computers.
Backdoor Trojans — This type of code allows other computer users to gain access to your computer across the internet. Here are examples of viruses, worms and Trojans released over the past couple years and a description of the havoc they raised:
DLoader-L — This Trojan arrived in a seemingly legitimate e-mail, and then it downloaded and installed another program on a PC. This program then allowed computers to be controlled by a third-party to attack websites whenever they connected to the internet, all without the PC owner's knowledge.
Bugbear-D — The worm recorded keystrokes, including passwords, and gave the virus writer access to them. The Compatable virus made changes to data in Excel spreadsheets. And the Sircam worm deleted and overwrote data on hard disks on a specified date.
Chernobyl (CIH) — This virus overwrote system BIOS chips on PCs, rendering them unusable. The Netsky-D worm made computers beep sporadically for several hours. And the Cone-F worm displayed a political message and mailed itself to other computers.
MyDoom — This worm e-mailed itself to addresses found on the infected computers. This generated so much e-mail traffic that e-mail servers slowed to a crawl or crashed. Companies responded by shutting down servers and mail service.