An unfortunate problem may be on the way. As adware, spyware and browser hijackers have become more sophisticated, antispyware programs have had to use more sophisticated means to catch them. Unfortunately, this may cause conflicts with antivirus programs using the same methods.
Antivirus programs historically have done a poor job of cleaning or even detecting spyware, although that has improved recently. Antispyware programs generally do not bother to detect viruses and trojans, since that is not in their mandate. For this reason, most people (sensible people anyway) have both antispyware and antivirus programs on their computer.
A very sophisticated, if low-level, technique used by antivirus software to catch viruses is to scan at the kernel level. The kernel is the lowest level of an operating system. By scanning at this low level, it leaves very little room for a virus to hide.
A number of antispyware companies are planning to introduce kernel-level scanning in their products. There really is no way to avoid it. The line between adware, spyware, viruses and trojans has virtually disappeared.
All of these types of parasites have poached each other's methods to replicate and to hide. Only the purpose of this unwanted software determines what it is called these days. The antispyware programs have to keep up, if they are to be of any use.
This is causing some concern in the antivirus industry. Two programs, both scanning at the kernel level at the same time, can crash a computer. Every antivirus company warns customers against using two different antivirus programs at the same time. People may end up having to make a hard decision: antispyware or antivirus?
The best way to avoid this potential problem may be cooperation between the antispyware and antivirus industries. An industry standard may have to be hammered out for kernel-level scanner drivers.
The kernel-level drivers can be written in such a way that, if more than one program is trying to access them, the drivers will juggle the requests to avoid a conflict. Two scanners would not be using the same resources at the same time and a system crash would be avoided.
The only other option would be for the antispyware and antivirus industries to encroach directly onto each other's territory. They would become direct competitors, with each side detecting both viruses and spyware.
As it stands now, antispyware programs do a poor job of detecting viruses and worms, while antivirus programs do only a fair job of detecting spyware. I don't see it as being in the best interests of the end users for each side to try and do the other's job. I hope the companies in both industries also see it that way and decide to work together.