Adware, it was loving awful and thank god malwarebytes exists bnecause without it that viurs would have killed that PC I used to use. It was a horrible experience there were ads everywhere, on google each search result had an ad right next to it and it was awful.
I remember downloading an image on google images one time and a lot of stuff started going crazy opening popups and virus stuff, spyware, etc. Then Kaspersky came in and said "Virus detected" and gave me the option to kill the virus and it did just that, saved that computer and got rid of the virus.