• Viruses - A computer virus is a type of malware that propagates by inserting a copy of itself into and becoming part of another program. It spreads bewteen computers in various ways, leaving infections and sometimes damage as it spreads. Nearly all viruses are attached to an executable file, which means the virus may simply reside on a system but will not be active or able to spread until it's opened. When the file is opened the viral code is executed as well. Usually the infected program keeps functioning after it is infected by the virus. However, some viruses overwrite other program files as they are opened with copies of themselves, destroying the host program altogether. Viruses spread when file they're attached to is transferred from one computer to another through a network, flash drive, cdrom, floppy disk, file sharing, or an e-mail attachment.
  
  
• Worms - A Worm is similar to a virus in that they replicate functional copies of themselves and can cause the same issues. In contrast to viruses, which require the manual spreading of an infected host file, worms are simple files that do not require a another program or human interaction to spread. To spread, worms either exploit a security flaw on the target system or use some trick of social engineering to get users to execute them.
  
  
• Rootkits - A Rootkit can be a single or multiple programs which are designed to take complete control of a computer. A hacker can use a Rootkit to give them administrative access to the computer from a remote location. Rootkits are very sophisticated as they are usually the toughest pieces of Malware to remove because they start before Windows starts and protects itself. A Rootkit infection often tries to replicate itself to other computers and also enslave them as zombies, forcing them to also attack other computers, steal sensitive information, display pop ups of fake anti-malware or other software or create spam.
  
  
• Trojans - Trojan's are another type of malware named after the wooden horse the Greeks used to infiltrate Troy. Trojans are a legitimately appearing but harmful piece of software. Users are often tricked into activating it on their systems. After activated, it can cause numerous issues on the infected computer, from irritating the user with pop ups, fake error messages, to damaging the host by deleting files, stealing data, or activating and spreading other malware, such as viruses. Trojans can also to create or open back doors giving hackers access to the computer without the users knowledge.
  
  
• Bots - A Bot is an malicious program that interacts with other network services. Simple Bots usually automate simple tasks that appear to be conducted by a human being such as completing forms on a web site or chatting online. Some bots are designed to lay dormant waiting for instructions from a central command center. A network of Bots is known as a "Botnet". Using this Botnet, hackers can activate these Remote Control these Bots and perform attacks against their target such as Web Sites. Bots can also log keystrokes, gather passwords, credit card, email spam, Bots can be considered smart Worms because they can be controlled remotely.
  

Malware can cause the following issues:

• Slow performance
• Internet Explorer errors or lockups
• Excessive “pop-up” advertisements
• Home page has changed
• Email or Internet access a lot slower
• System lockups