Usually we download apps from Google Play Store with thoughts that our phones are safe and downloading a lot of new applications don't have disadvantages apart from taking a lot of internal storage from our devices. As it turns out downloading applications which are not necessary for us may cause a lot of problems connected with our actions on phone.
Google by using their security system and special machine which is programmed for fighting with dangerous apps detected 300 apps which apart from their simple main role like file exploration had hidden role - they were used as bots set for DDoS attacks. How estimates Google, over 70 000 devices may have been infected by these malware. It's possible that soon Google will detect more harmful apps available for download from the Google Play Store.