this did not happen on chrome, internet explorer,or pale moon only firefox so that makes me wonder if it was not just firefox http://en.wiktionary.org/wiki/-ware#Derived_terms_2- - - i dont know what malware is
Let's start with some terminology:
- -ware, suffix used to describe types of computer components, like in hardware, software and the following subspecies of software
- Malware is anything that can harm your computing experience, covering viruses, adware, crapware, greyware, spyware and whatnot.
- Adware, as the name suggests, is something that will make you see marketing related things like underlined words, popups and strange search results
- Crapware may not be a threat, but it won't work as supposed
- Greyware is something you don't necessarily have the rights to possess
- Spyware is something that collects and resends information about you. Connected with adware it can be used to determine what kinds of ads would interest you. In a more dangerous form it can sniff your passwords and credit card data.
Wiktionary has quite a comprehensive list about -wares:
http://en.wiktionary.org/wiki/-ware#Derived_terms_2To your question about why only Firefox was affected... One reason is that browser add-ons don't usually inherit, meaning that if you have some add-on installed in one browser and you install another browser, the new one will be clean. Viruses are another matter, they will spread all over of your computer.
The reason why AVG and most other anti-virus programs don't notice many kinds of malware is that most of them aren't viruses. Actually Norton was some years ago threatened by a lawsuit unless they dropped their adware protection down, because preventing ads to show would have a negative affect to the income of the advertisers!
Actually, you might have some kind of adware already preinstalled in a new brand computer! And you may get some more just by updating some software unless you carefully uncheck their optional offers.