This is annother argument I won't pretend this is the end all.
First to introduce the players (as I see them)
Virus experts: Experts in name only they have no better understanding of viruses than anyone else.
Thies are people who proffit from the sale of anti-virus software.
Unix experts: Not security experts. Experts in how Unix works. The first people to clame Unix is imperveous to viruses.
Security experts: Experts in the security field. Has nothing to do with the virus industry.
What is a virus: A virus is a program that sneaks into your computer by piggybacking on other software.
Once in your system the virus installs itself into other programs on your system.
Unix immunity: Unix software is installed into a secured area of the hard disk. From this area programs can be run but not modifed.
The security defect: There is the argument that a virus could use a security defect to infect a Unix computer. This has been demonstrated and dose work.
However this means the virus has a short window of time when it may infect a computer.
This is very much like the short window of time a virus may infect an antivirus protected system.
With Unix a virus may strike anytime before the defect becomes known. Once the defect is known the virus is nolonger able to infect.
With Windows a virus may strike any system before the virus is known. Once the virus is known the virus may still strike any system not protected by antivirus software.
The defect permitting the virus may be cought and fixed before the virus is known however if it isn't once the virus is known the defect is also known and will be fixed before antivirus software has a chance to make any diffrence.
In short Unix security provides far suppereor protection against viruses than antivirus software. Enough so to make creating Unix viruses far more work than they are worth.
Unix security vs antivirus for protecting against worms.
Worms reguardless of Unix or Windows require a significant software defect to happen.
Antivirus software can not prevent worms from infecting the system and once infected the worm can disable the antivirus software.
Under a properly secured Unix system if a worm dose slip into the system it will likely have restricted access and will be unable to do much damage. Rebooting often flushes the worm from the system.
Also a worm dose it's worst inside an hour of being first release long before a bugfix or signture can be released.
In short Not only do Unix systems have a solution for Unix viruses it's a far better solution than using antivirus software.
Should that change the is already open source antivirus software. Just in case.
Besides windows e-mail infections pass through Unix e-mail servers. There is no better way to deal with e-mail infections than antivirus software. Especally before the e-mail can reach the Windows user.