Malware

means malicious software – software created to damage or alter data.

Viruses, worms and Trojan Horses are all malicious programs that can cause damage to your computer, but there are differences among the three, and knowing those differences can help you better protect your computer from their often damaging effects.

• A computer virus

  attaches itself to a program or file enabling it to spread from one computer to another, leaving infections as it travels. Almost all viruses are attached to an executable file, which means the virus may exist on your computer but it actually cannot infect your computer unless you run or open the malicious program. It is important to note that a virus cannot be spread without a human action, for example by sharing infecting files or sending emails with viruses as attachments in the email.

• A worm

  is similar to a virus by design and is considered to be a sub-class of a virus. Worms spread from computer to computer, but unlike a virus, it has the capability to travel without any human action. The biggest danger with a worm is its capability to replicate itself on your system. One example would be a worm sending a copy of itself to everyone listed in your e-mail address book. Then, the worm replicates and sends itself out to everyone listed in each of the receiver's address book, etc. Due to the copying nature of a worm and its capability to travel across networks the end result in most cases is that the worm consumes too much system memory, causing Web servers, network servers and individual computers to stop responding.

• A Trojan Horse

  at first glance appears to be useful software or files from a legitimate source. When a Trojan is activated on your computer, the results can vary. Some Trojans are designed to be more annoying than malicious (like changing your desktop, adding silly active desktop icons) or they can cause serious damage by deleting files and destroying information on your system. Trojans are also known to create a backdoor on your computer that gives malicious users access to your system, possibly allowing confidential or personal information to be compromised. Unlike viruses and worms, Trojans neither reproduce by infecting other files nor self-replicate.

• A blended threat

  is a more sophisticated attack that combines some of the worst aspects of viruses, worms, Trojan horses and malicious code into one single threat.

• Spyware

  is software designed to collect information for commercial or criminal purposes. It usually comes hidden in fake freeware or shareware applications downloaded from the Internet. It can gather information about e-mail addresses and even passwords and credit card numbers. Because spyware exists as independent executable programs, they have the ability to monitor keystrokes, scan files on the hard drive, snoop other applications, such as chat programs or word processors, install other spyware programs, read cookies, change the default home page on the Web browser, consistently relaying this information back to the spyware author who will either use it for advertising/marketing purposes or sell the information to another recipient.