do anti-virus companies create viruses?

That question has been pondered since the beginning of AV software. I would not be in the least supprised if they did, and made it so that only their software removed it.

E.G. Symantec making Virus that McAfee cannot fix

It must be true. If I were a car mechanic, at nights I would go for a walk and with a hammer to crash some car. :)

The simple answer to this is yes

For a long time it was a major selling point for anti-virus products to recognize the signature of more viruses than their competitors.

The achieve this it was common practice for internal engineers to create variations of actual viruses, which could then be added to the list of viruses known to the software.

This was a valid process to a point as it was quite possible that the original virus could be mutated in the world outside the lab

This led to claims that a AV suite protected against many thousands of different infections but with a much lower number of those "In the Wild"

With the move to heuristics in the industry where the actual activity of the virus is looked for rather than a key piece of code this is done a lot less today.

MYTH CONFIRMED

Thanks for shedding some light on a question I have been asking myself for quite some time.

A lot of bogus security software and fake spyware removers are on the Internet.

These are actually 'hijackers'. Some contain rootkits some are DNS changers, some are backdoor Trojans that steal passwords and personal (critical indentification) information.

If you don't know if one of these programs is legit, it's best to ask someone about it before running a scan and getting caught with it taking over your computer.