Malwarebytes security researcher Pieter Arntz takes a look back at the early 2000s when he was not employed in the cybersecurity industry but was part of a group of expert helpers that volunteered their time to help victims remove adware and malware from computers. Adware, browser hijackers, dialers, spyware, and ad injectors were for the most part not detected by mainstream security software. Many AV companies just ignored them to avoid the risk of a lawsuit. As a consequence, many PC users flocked to online help-forums to ask for assistance in getting rid of unwanted pop-ups, pop-unders, and browser windows.
Source: https://www.bleepingcomputer.com/news/security/the-adware-families-that-changed-the-antivirus-industry/