What is a Computer Virus?

A computer virus is so called because its modus operandii of infecting computers is analagous to a biological virus infecting animals. A computer virus is a program that that transmits itself from computer to computer via email or buy attaching itself to executable files. Some viruses are very destructive, causing irreperable damage to software and occasionally hardware. However, the most destructive viruses are less infectious, as computers which no longer work are not able to transmit them. Thus the majority of viruses are just an irritation, displaying messages or slowing down the operation of your machine.

What different types of virus are there?

Viruses can be grouped into a number different categories, depending on how they work. Broadly speaking, these categories include:

• Boot sector viruses - these alter the boot sector on a hard drive and were typically transmitted by the use of floppy disks. They are less prevalent now.
• email viruses - these are now very common. Typically they forward themselves to every email address in an Outlook or Outlook express address book. Some even work by scanning for email addresses on websites and forwarding themselves automatically in this way.
• Time bombs - they stay dormant until a predefined time, when they then execute.
• Macro - these viruses are transmitted via Microsoft Office programs including Word and Excel.
• Trojan Horse - these viruses purport to offer something, eg a screensaver. However, once opened by the user their payload is activated. These are not viruses in the true sense as the user must click on the file or download something in order for it to execute.
• Worm - worms exploit gaps in security on networks and replicate themselves in this way. They are often in the form of macros inside Microsoft Office documents.

More information on viruses and the latest security threats can be found on the Symantec web site.

What is Spyware ?

Spyware is a type of malware that can take partial control of the user's computer for the benefit of a third party. It's operations can include:

• Sending details of the user over the internet to a third party. In the worst case scenarios, this can include keeping a note of logon details typed in to access, for example financial websites, and transmitting these details to criminals abroad. Less malicious uses include the transmitting of details of sites visited and links clicked for use by online advertisers.
• Taking over the search function on your computer, so that instead of visiting for example, Google, you are diverted to a search engine specially set up to divert traffic to its advertisers.
• Other types of spyware launch unasked for popup windows, relevant to what the user is searching on.

Spyware can be installed on a computer if you visit a site that takes advantage of security holes in Internet Explorer. Alternatively, spyware is bundled along with free software that can be downloaded. It is important here to also mention the term "Adware". Adware is a type of spyware that displays advertisements targetted at the surfer. Adware is not always installed without the user's consent. For example, it may be installed as part of a free software package to avoid having to pay registration fees.

Many sites employ the use of "cookies" to track internet usage for statistical purposes, or to aid the login process to secure sites. In my view, this use of cookies does not constitute spyware - a cookie is merely a text file - it does not execute, divert traffic or display advertising, and has many beneficial uses such as remembering details of your last visit so that you do not have to log in again.

For more details on Spyware, visit Microsoft.