Around eight potentially unwanted applications (PUAs) have been discovered on the Microsoft Store that use a victim's computer to mine cryptocurrency.
The apps, which included those for computer and battery optimisation, internet search, web browsers, and video viewing and download and came from three developers: DigiDream, 1clean, and Findoo, according to a blog post by security researchers at Symantec,
The researchers said that as soon as the apps are downloaded and launched, they fetch a coin-mining JavaScript library by triggering Google Tag Manager (GTM) in their domain servers.
"The mining script then gets activated and begins using the majority of the computer's CPU cycles to mine Monero for the operators. Although these apps appear to provide privacy policies, there is no mention of coin mining on their descriptions on the app store," researchers said.
When each app is launched, a web domain is silently visited in the background and triggers GTM with the key GTM-PRFLJPX, which is shared across all eight applications.
Researchers said that while GTM is a legitimate tool that allows developers to inject JavaScript dynamically into their applications, these malicious developers abused this to conceal malicious or risky behaviours.
The apps were put on the app store between April and December 2018, the investigation found. And while the apps were only on the store for a short time, a significant number of users may have downloaded them. Researchers said that there were almost 1,900 ratings posted for these apps.
The apps in question are Fast-search Lite, Battery Optimizer (Tutorials), VPN Browsers+, Downloader for YouTube Videos, Clean Master+ (Tutorials), FastTube, Findoo Browser 2019, and Findoo Mobile & Desktop Search apps. Researchers said that they have informed Microsoft and Google about these apps, and they have since been removed from the store.
The mining JavaScript has also been removed from Google Tag Manager.
The news comes at a time when app stores are coming under increased pressure to improve the effectiveness of their app vetting procedures. Google's Play Store has long been criticised for hosting malicious applications, including those that host so-called 'cryptojacking' code and spyware.
