• Viruses -A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc.
  
  
• E-mail Viruses - An e-mail virus moves around in e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book.
  
  
• Worms - A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well.
  
  
• Trojan horses - A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically.

Spyware

Spyware installs itself onto a user's computer by stealth, subterfuge and/or social engineering and sends information from that computer to a third party without the user's permission or knowledge. Spyware includes keyloggers, backdoor Trojans, password stealers, and botnet worms, which cause corporate data theft, financial loss and network damage. Protection from spyware is an integral feature of our integrated security solutions, and is detected in the same way as viruses, Trojans and worms.

Adware and potentially unwanted applications (PUAs)

Adware displays advertising - such as pop-up messages - which affects user productivity and system efficiency. Although many people view adware as undesirable, it is also a key component of a business model that can bring value to consumers in exchange for receiving advertisements.

PUA is a term used to describe an application that is not inherently malicious, but is generally considered unsuitable for the majority of business networks. Potentially unwanted applications include adware, dialers, remote administration tools and hacking tools.

Symptoms of spyware or virus infections:

• PC will not boot correctly or at all
• Slow PC performance when opening programs or saving files
• Unwanted pop-up windows
• Browser homepage hijacked
• Repeated change in your browser's home page
• Random error messages
• New and unexpected toolbars in your browser