Avast Mobile Security, also known as Avast Mobile Security & Antivirus, has more than 100 million downloads and a solid 4.5 user rating in Google Play, and it was our Editor's Choice for Best Android Security App in 2014 and 2015. We liked its huge assortment of powerful anti-theft and privacy tools (including some for rooted phones only), and its good, if not quite perfect, malware-detection rate.
Avast's mobile protection has gone through some changes in the last couple of years. Things got a little bumpy in our testing last year, when the app went to a completely free ad-supported model but lost ground with a lower malware-detection rate and heavier system impact. Avast even discontinued a few of our favorite unique features.