Getting Rid of Adware on Your Mac
Although AdwareMedic functions somewhat like anti-virus software, it’s important to understand that it is not anti-virus software!
and further down:
Using AdwareMedic will not prevent you from being "infected" with adware again in the future. For that matter, neither will using anti-virus software; only a change in your online habits can keep you safe.
If you think you've got some Adware [footnote] Adware is any software package which automatically renders advertisements in order to generate revenue for its author. [/footnote] on your Mac, Adware Medic is free to download - donations accepted.