Does the app access the Internet to connect to the game servers and other gamers? The problem may be due to this connection. Here's something you can try. Connect to iTunes and do a full backup of your iPhone. Then, after disconnecting from iTunes, delete the game and download it again. This will delete all game data and game progress, which is why you did the backup first. If the re-installed game now works perfectly, you know the problem was, at least partly, in the game data. If that is the case, you'll have to start over again, without restoring from your backup. If the problem still persists, you can restore from the backup, as the malware is coming in through the game developer's servers. Probably disguised as a legitimate ad.