Google desperately needs to curb the spread of Android malware. In September alone, researchers uncovered a total of 172 infected apps on the Play Store. The worst part? These apps had racked up over 335 million installs by the time they were detected by security experts.

Adware accounted for a staggering 300,600,000 installs, according to data complied by ESET malware researcher Lukas Stefanko. Other types of malware found on Play included subscription spam, hidden ads, and SMS premium subscription software. Interestingly, while there were 57 instances of software with hidden ads, they made up less than 5 percent of all installs.