A collection of 151 scam apps have been discovered and removed from the Google Play Store, but Android users need to check they don't have any of them installed (or did in the past).

As BGR reports, the cybersecurity software company Avast recently discovered a widespread premium SMS scam operating on the official Play Store. Avast has dubbed it the UltimaSMS campaign (because the first scam app the firm discovered in its investigation was Ultima Keyboard 3D Pro), and it consists of 151 fake apps that have been downloaded over 10.5 million times in more than 80 different countries.

The apps disguise themselves as legitimate tools across multiple app categories including custom keyboards, QR code scanners, video and photo editors, spam call blockers, camera filters, and games. However, they all ultimately have the same aim of signing users up to premium SMS services.

Each app follows the same pattern: Once installed, the phone's location, International Mobile Equipment Identity (IMEI), and phone number are checked to discover the area code and language to use. Prompts then ask the user for their phone number and sometimes their email address, too. This information is then used to subscribe the user to premium SMS services without them realizing. The charges are typically $40 or more a month and it can take weeks or months for a user to realize.

Once an UltimaSMS app has achieved its goal it either stops working or offers more subscription options rather than the promised functionality it was downloaded for. The problem is, even if a user uninstalls the app at this point the premium subscriptions will continue to take money from their accounts.

Avast created a list of all 151 apps that are part of this scam, and they are listed in the chart below; every Android user should take a look. If you have any of these apps installed (or did in the past), uninstall them immediately, but also check your statements and contact your carrier if you spot any unusual charges. It should also be possible to ask your carrier to disable premium SMS options on your account if you want to avoid this type of scam in the future.