Avira – AVG – Avast – Kapersky – ESET NOD32
Spybot S&D – Malwarebytes – SuperAntiSpyware
OK, there are others BUT
The decent ones never produce unsolicited popups which warn of multiple infections UNLESS you have one of the above installed..
Neither do they appear as ads every time that you go to any webpage..
Just because an ad appears on the webpage of some IT professionals does not mean that the program has any merit. Some of the ads are most decidedly crapware. The IT professionals should know better and clean up their act.
If you are not sure about a program, go to a newsgroup or forum and ask BEFORE you attempt an installation..