As has been explicitly mentioned several times before...
viewtopic.php?f=6&t=486913&p=11063269#p11063269viewtopic.php?f=6&t=514313&p=11788735#p11788735CS has no viruses, whatever you are becoming infected by is obviously getting through whatever 'security' you have in place, or you are recieving them from other tabs/windows you have open. Get an anti-spyware and anti-virus running and sort it out, there are plenty free ones about. Avast is an excellent free anti-virus, and Malawarebytes Anti-malware is a good anti-spyware program. There are others i'm sure that could do just as good a job.
If CS had viruses, everyone would be complaining about them, but since it is just a select 1 or 2 every blue moon, it can't be server-side.