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.

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,  vendors now make life 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.

Microsoft have introduced stronger protection in their Windows 7 and Windows 8 products 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, Smartphones 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.