The Bread malware for Android is also called Joker. But no matter the name, its authors have proven themselves to be unrelenting in their efforts to avoid being first discovered by and then dumped from Google's Play Store.
Alec Guertin and Vadim Kotov, of the Android Security & Privacy Team, blogged recently about the extended conflict between the two parties that has been going on since 2017.
Bread/Joker began with one specific fraud method in mind (SMS billing) and then changed to toll fraud. SMS fraud gets a victim to pay for unwanted products or services by messaging to a specific number via SMS.
Bread changed its method of fraud after Google introduced new policies that restricted use of the SEND_SMS permission by an app.
Toll fraud connects to malicious payment pages through a device's WAP connection. The payment is then automatically charged to a device's phone bill.
Google notes the underlying problem that can be exploited by the threat actors when it explains in the blog that "Both of the billing methods provide device verification, but not user verification. The carrier can determine that the request originates from the user's device, but does not require any interaction from the user that cannot be automated. Malware authors use injected clicks, custom HTML parsers and SMS receivers to automate the billing process without requiring any interaction from the user."
The malware authors employed many differing programming techniques to try and sneak the malware past the defenses of the Play store. Not only that, as soon as one version was removed they tried to send a new and slightly different version of the malware.
Google says with some exasperation that, "At peak times of activity, we have seen up to 23 different apps from this family submitted to Play in one day. At other times, Bread appears to abandon hope of making a variant successful and we see a gap of a week or longer before the next variant. This family showcases the amount of resources that malware authors now have to expend."
Google found the authors tried "versioning" to a great extent, an abuse tactic that is unique to app stores. They saw that some apps started with clean versions, in an attempt to grow user bases and build the developer accounts' reputations. The user is unaware of the potential for fraud in the clean version, since it does not happen.
At some point, the malicious is code introduced through an update. Google found that some of the early "clean" versions would contain varying levels of signals that the updates will include malicious code at a later point.
Google's effort against Bread have stopped 1,700 apps from being downloaded by users according to their figures.
— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.