Every time I unlock my tablet, I'm shortly redirected to an ad (usually to dating sites or "I'm A Lucky Winner!" sites) even if I'm not on a search engine. When I hold the home button, then go back into the app I was on, the ad disappears. Virus detectors didn't spot anything. My battery drains faster than ever, but I'm not sure the ads are responsible. Nothing too harmful has happened, but I'd like to remove this problem just in case something more serious happens. Thanks!