Besides a faster draining battery and a sluggish phone too hot to the touch, there are other ways to discover whether your phone is carrying an app that is a DrainerBot. You can look for apps that have used a large amount of data each month. On Android 9 Pie, you can find this by going to Settings > Network and Internet > Data Usage > App Data Usage. Apps that are DrainerBots consume multiple GBs of data on a monthly basis.
An SDK from a company from the Netherlands called Tapcore helped distribute the DrainerBots, according to Oracle. The company provides software that allows developers to monetize pirated installations of their apps. In a blog post written to defend itself from the accusations, the company says, “At the moment of first hearing about the DrainerBot ad fraud scheme, Tapcore began immediate internal investigation to see whether any such code was ever distributed through its network without its knowledge. The company is ready to cooperate with all interested parties and provide all results on its findings. Openness and transparency is paramount in the mobile advertising industry, and Tapcore is prepared to share all data and results.”
Google has reportedly removed all of the offending apps except for one, Solitaire: 4 Seasons (Full), which you should obviously avoid. If you already have it installed, uninstall it immediately.