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Joker Malware Found In 24 Apps In Google Play Store

Security researcher Aleksejs Kuprins of CSIS cybersecurity services company has discovered 24 apps which have been available for download in the Google Play Store that contain ‘Joker’ malware.

What Is Joker Malware?

Joker malware is a spy and premium subscription bot that makes money by simulating clicks. If, for example, a Joker infected app is downloaded, the malware delivers a second-stage component which silently simulates the interaction with advertisement websites, and steals the victim’s SMS messages, their contact list and their device information.

One of the silent automated interactions with advertisement websites includes simulation of clicks and entering of the authorisation codes for premium service subscriptions.

One specific example of what Joker can do, given by Mr Kuprins on the CSIS tech blog is that in in Denmark, Joker can silently sign a victim up for a 50 DKK (6,71 EUR) per week service by automating interaction with a premium offer’s webpage, entering the offer code, waiting for a SMS message with a confirmation code and extracting it, and finally submitting the code to the offer’s webpage to authorise the premium subscription.

Which Apps?

The 24 apps harbouring the ‘Joker’ malware, which have been installed more than 472,000 times are: Advocate Wallpaper, Age Face, Altar Message, Antivirus Security – Security Scan, Beach Camera, Board picture editing, Certain Wallpaper, Climate SMS, Collate Face Scanner, Cute Camera, Dazzle Wallpaper, Declare Message, Display Camera, Great VPN, Humour Camera, Ignite Clean, Leaf Face Scanner, Mini Camera, Print Plant scan, Rapid Face Scanner, Reward Clean, Ruddy SMS, Soby Camera and Spark Wallpaper.

Only Targets Certain Countries

The good news is that ‘Joker’ malware only attacks targeted countries and that most of the infected apps contain a list of these targeted Mobile Country Codes (MCC) meaning that the victim has to be using a SIM card from one of these countries to receive the second stage payload.  The bad news is that the UK is one of those targeted countries.

Google On Top Of Things

Despite there being 24 apps identified so far, Mr Kuprins has reported that Google has stayed on top of things during his investigation and has been removing all the offending apps without the need for prompting.

Not The First Time

Back in January last year, Security researchers discovered 36 fake and malicious apps for Android that could harvest data and track a victim’s location, masquerading as security tools in the trusted Google Play Store.

What Does This Mean For Your Business?

Google Play is a trusted source for apps, and it’s worrying that hundreds of thousands of customers may have the affected apps from Google Play.  In this case, Google has responded relatively quickly and has deleted infected apps where they have been found. 

The obvious advice to android phone users is to check the list of infected apps and delete any on your phone that match. If you think you may have been affected by Joker via an app it may be a good idea to check your Google Play account for any unauthorised subscriptions, check your credit card or bank statements as far back as June of this year, and let your contacts know that you may have been infected (because Joker steals your phone’s contact list). 

To minimise the risk of falling victim to damage caused by fake apps, users should check the publisher of an app, check which permissions the app requests when you install it, delete apps from your phone that you no longer use, and contact your phone’s service provider or visit the high street store if you think you’ve downloaded a malicious/suspect app.

This latest discovery of infected apps on Google’s Play Store should prompt the company to make even greater efforts to police the apps that it offers there.


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