A malicious self-downloading app is infecting Android phones in the US., U.K. and France. "Ks Clean," which masquerades as a device-cleaning application, displays a fraudulent system update that freezes smartphones until owners select "OK." Once a user gives the app access to his device, an APK (Android application package) installs itself and asks for administrator privileges. Then, the Android phone is inundated by pop-up ads, which will even appear when the owner is using other apps. Removing "Ks Clean" is difficult, since the malware has been granted admin rights.According to San Jose-based cybersecurity firm Zscaler, more than 300 incidents of malicious APKs "from this campaign" have been identified during the past two weeks. The malware is obtained through deceptive advertisements posted on forums.To avoid downloading "Ks Clean," disable the auto-download feature on your Android's mobile browser and switch off the "unknown sources" option in its settings. Malware targeting Android-based smartphones is on the rise - the Google-developed operating system is "more open and adaptable," says security software company Sophos. As of last spring, an estimated 1.3 to 1.4 billion people across the world owned Android phones.