It is common knowledge that freeware cannot stay afloat unless it's ad-supported or promotes third-party services. This trait is being heavily taken advantage of as far as adware distribution goes. DNS Unlocker does not spread by encouraging potential clients to give its remarkable functionality a shot – instead, it accompanies other free products' installation. Some computer games, educational video creation tools and multimedia solutions go with this adware already built into their setup, therefore by agreeing to the terms of service for the former you also opt into the latter, often without even realizing it.
Ads by DNS Unlocker are generated by the aggressive browser helper object installed by the virus. It makes random chunks of text on websites appear all in capital letters and hyperlinked, with popups automatically showing up as you put your mouse pointer on those keywords. There will also be numerous banners and comparison shopping objects all over the place, regardless of the web page that's visited. Interstitial ads won't fail to get constantly triggered either. Stopping this frustrating commercial onslaught is manageable via ad hoc steps meant to thoroughly eliminate the potentially unwanted program.