Rash of porn clicker trojans sneak past Google Play review process

Google is having difficulties keeping a wave of trojan 'porn clickers' out of the Google Play app store.

According to security firm ESET, trojanised fake versions of dozens of popular apps have been installed over 200,000 times from the Google Play store in the last two months, all with the aim of jacking up clicks to porn sites.

The company noted that the app didn’t directly harm a user, say by stealing information, but could have knock on effects to their monthly data usage and bills. In any case, the apps do violate Google Play developer policies and shouldn’t be on the store.

Google has been battling the porn clicker trojans since May, with a fake version of the popular app Dubsmash gaining over 100,000 installs, ESET reported at the time.

The real Dubsmash app, which has been installed on up to 100m devices, lets users pick a familiar sound and record an accompanying selfie to be sent to friends. Malware authors have been riding its popularity by publishing fake apps like Dubsmash 2, Dubsmash 3 and now dozens of other apps.

As noted by security firm Zscaler in June, initially the fake apps included encrypted hardcoded porn URLs while newer variants dynamically retrieve porn URLs from a remote server.

The troubles also follow Google earlier this year stepping up efforts to protect users by adding a team of human experts to its review process to keep the store free of apps that violate its developer policies without sacrificing the speed developers can have their apps available to consumers. Google wants developers to expect that to happen within hours of submission rather than days or weeks.

But the speed of publishing on Google Play may be the problem in this case. According to ESET, Google was playing whack-a-mole with the authors of the Dubsmash 2 trojan through the end of May, with apps carrying the same malicious code uploaded to the store five times within five days, suggesting the attackers may have found a way to bypass Google’s automated malware detection system, Bouncer.

“It’s very rare for malware to be uploaded to official Play Store with the same functionality so many times over such a short period,” noted ESET researcher Lukas Stefanko.

Stefanko on Thursday said it had now detected a further 51 trojan porn clickers that are available on Google Play with four gaining over 10,000 installs while another, Subway Surfers 2, landing over 50,000 installs. The latest rash of trojan apps brings ESET’s total count to 60 that it’s found in Google Play in the last two months.

The attackers have also targeted several other popular apps to dupe Android users into installing them, including Download Manager, Pou 2, Clash of Clans 2, Subway surfers 2, Subway surfers 3, Minecraft 3, Hay Day 2, game cheat apps and video downloaders.

“ESET is still seeing occurrences of this infiltration on Google Play and, after more than a month, these fake Trojan Clickers are still managing to evade Google’s Bouncer malware filter and potentially exposing millions of users to risk,” Stefanko noted.

“Google has pulled the malware from the Play Store and also reports some of them as potentially harmful applications using its built-in security service,” he added.

This article is brought to you by Enex TestLab, content directors for CSO Australia.

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