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A recent analysis by DoubleVerify engineers has identified a trend in mobile advertising known as AfterCall ads, where applications display advertisements immediately after a phone call ends. This practice generates hundreds of millions of impressions monthly and raises concerns about user experience and brand integrity. AfterCall applications operate using three components: a misleading permission, a Broadcast Receiver to capture end-of-call events, and an Activity to display ads. The SYSTEMALERTWINDOW permission allows these apps to show content over others, often granted under false pretenses. They utilize Android's telephony system to trigger ads post-call and employ tactics to obscure their presence, such as removing themselves from the recent apps list and using innocuous icons. Detection is challenging due to the lack of shared codebases and the obfuscation techniques used. The scale of the issue is significant, with numerous AfterCall applications identified monthly, negatively impacting user experience and raising concerns for advertisers.