Today, we are publishing a report on the security risks present on Android app markets in the first half of this year. The report presents trends in malware and madware, the latter referring to apps that use aggressive ad libraries. Ad libraries have the ability to collect information about the app’s user in order to serve targeted advertisements. However, some of these libraries can leak personal information or exhibit annoying behaviors such as displaying ads in the notification bar, creating ad icons or changing Web browser bookmarks. We refer to these libraries as aggressive ad libraries. In the middle of this year, 65 ad libraries were known and over 50 percent of them were classified as aggressive. The percentage of apps that use aggressive ad libraries has been on the rise since 2010, increasing every year, and reached 23 percent in the first half of 2013. According to our report, users can expect the most madware when downloading apps from the Personalization category, followed by the Utilities & Demo category and the Racing Games category. This contrasts with the presence of malware, which is most likely to be found in the Photography, Arcade & Action Games and Entertainment categories. Malware, as expected, is on a steady rise, with the volume of known malware samples (excluding madware and grayware) reaching almost 275,000 in June 2013 and recording a four-fold increase from June 2012. The Mobile Adware and Malware Analysis report is available now.