Malware includes Trojans and other things that aren't viruses (they don't replicate themselves to other phones - but they might be sending your contacts - or your passwords - to the developer), so you should have at least one malware app running, as well as one anti-virus app running. But a popup preventer? You can set your browser up to prevent that. (Adware that pops up when you're not using a browser may or may not show up as malware, but it usually comes from visiting infected sites or opening infected emails - so don't do those things.)