The computer virus threat comes mainly from Internet email, although even trusted suppliers, clients friends and employees may inadvertently bypass anti-virus measures.

At the desk-top there are several vendor products that protect the user against known viruses. Some suppliers provide an heuristic mechanism to detect “virus-like” code.

With all such protection it is imperative to keep the defences up to date. With tens of new viruses every week and a major risk about once a month, this can be a time consuming bore for most users. Some vendors now make this easier by automated updates. However once an infection has bypassed the controls, the damage may remain undetected for days or months.

For the larger companies the best solutions for anti-virus measures probably lie with an external service provider so that infected email never arrives in the first place. However email from the Internet is not the only source of possible infection, so desk-top measures must also be in place.

The Internet also provides web based email as well as web surfing which can be exploited to drop a virus into your machines via unexpected back doors.

There is therefore the need for newer products that make life more difficult for the attacker by patrolling the doorway between your computers and the outside world.

Desk-top protection should now include “sand-box” techniques that ensure Internet derived code runs in a controlled way on your PC.

Microsoft have introduced stronger protection in their Windows XP product but they continue to announce updates to close those doors that allow intruders to enter without invitation. MAC also has its viruses as does Linux, Palm Tops and other mobile devices.

Today Junk mail has become as damaging to business - most of us will want the Internet Service Providers (ISP) to solve this issue.