Trojan Horse: This is a program so you may download from Internet. You think this will help your computer but in the reality it will harm your computer and it can download stuff without you knowing anything about it. This kinda programs are often contain back-doors so the attacker can get access to your computer. To get an Trojan Horse you must download it. What can a Trojan do? Steal Information. Delete files. Downloading Software so contain viruses. Remote Access. Cracking attack. randomly shutting down your computer. lower security settings on the computer. May do DoS (Denial of Service) attacks. Worm: This is a programs so self replicating they use networks and E[*]mail to infect computers. Worm spread to computer to computer by them selfs when you are infected by a Worm they may use your E[*]mail to mases spam copy of them selfs to your friend list. They uses Instant Links, attachment in mail and IRC rooms may also be used to trick the victim. What can a Worm do? Sends E mails without you knowing anything about it. Uses your E mail address to mases spam companies and private persons with junk mails. May make back door on the victims computer to make it a Zombie computer. Downloading Malicious Software. Virus: They are designed to copy them selfs in big numbers on the victims computer without the user knowing anything about it. They can use spread them selfs to other computer by using CD rooms and floppy Disks. They can delete files and also modify them selfs. So lets say you delete the Virus file but it will still come back. What can a Virus do? Spike your CPU usage. Copies them selfs in large number. Infect a specific file type. ect. (*.txt) infect CD and floppy disks to spread to other computers. Delete files. Rogue Software: This is a program so are using Malicious Software It may download programs without you knowing anything about it. This kinda program are designed to give false scan results. They want you to buy their programs so you can fix your problems that they deceted. So everything the scan says is just made up so you should believe that your computer is having big issuse. What can a Rogue Software do? False scan result. Aggressive Advertising. Change your homepage. Pop up windows. Downloading Software.