Mysterious family of malware hid in Google Play for years

A mysterious household of Android malware with a demonstrated historical past of successfully concealing its myriad spying actions has as soon as once more been present in Google Play after greater than two years of hiding in plain sight.

The apps, disguised as file-sharing, astronomy, and cryptocurrency apps, hosted Mandrake, a household of extremely intrusive malware that safety agency Bitdefender called out in 2020. Bitdefender stated the apps appeared in two waves, one in 2016 by way of 2017 and once more in 2018 by way of 2020. Mandrake’s potential to go unnoticed then was the results of some unusually rigorous steps to fly below the radar. They included:

• Not working in 90 international locations, together with these comprising the previous Soviet Union
• Delivering its last payload solely to victims who have been extraordinarily narrowly focused
• Containing a kill change the builders named seppuku (Japanese type of ritual suicide) that absolutely wiped all traces of the malware
• Absolutely practical decoy apps in classes together with finance, Auto & Autos, Video Gamers & Editors, Artwork & Design, and Productiveness
• Fast fixes for bugs reported in feedback
• TLS certificate pinning to hide communications with command and management servers.

Lurking within the shadows

Bitdefender estimated the variety of victims within the tens of 1000’s for the 2018 to 2020 wave and “most likely a whole lot of 1000’s all through the complete 4-year interval.”

Following Bitdefender’s 2020 report, Mandrake-infected apps appeared to fade from Play. Now, safety agency Kaspersky has reported that the apps reappeared in 2022 and went unnoticed till now. Apart from a brand new spherical of decoy apps, the Mandrake operators additionally launched a number of measures to higher conceal their malicious habits, keep away from evaluation from “sandboxes” utilized by researchers to establish and examine malware, and fight malware protections launched in recent times.

“The Mandrake adware is evolving dynamically, bettering its strategies of concealment, sandbox evasion, and bypassing new protection mechanisms,” Kaspersky researchers Tatyana Shishkova and Igor Golovin wrote. “After the functions of the primary marketing campaign stayed undetected for 4 years, the present marketing campaign lurked within the shadows for 2 years, whereas nonetheless obtainable for obtain on Google Play. This highlights the risk actors’ formidable abilities, and likewise that stricter controls for functions earlier than being revealed within the markets solely translate into extra subtle, harder-to-detect threats sneaking into official app marketplaces.

A key characteristic of the newest era of Mandrake is a number of layers of obfuscation designed to stop evaluation by researchers and bypass the vetting course of Google Play makes use of to establish malicious apps. All 5 of the apps Kaspersky found first appeared in Play in 2022 and remained obtainable for at the least a yr. The newest app was up to date on March 15 and faraway from the app market later that month. As of earlier this month, not one of the apps have been detected as malicious by any main malware detection supplier.

One technique of obfuscation was to maneuver malicious performance to native libraries, which have been obfuscated. Beforehand, Mandrake saved the malicious logic of the primary stage in what’s often known as the applying DEX file, a kind of file that’s trivial to investigate. By switching the placement to the native library libopencv_dnn.so, the Mandrake code is tougher to investigate and detect as a result of the native libraries are harder to examine. By then obfuscating the native library utilizing the OLLVM obfuscator, Mandrake apps have been much more stealthy.

The chief functions of Mandrake are to steal the consumer’s credentials and obtain and execute next-stage malicious functions. However these actions are carried out solely in later-stage infections which are served solely to a small variety of fastidiously chosen targets. The first methodology is by recording the display screen whereas a sufferer is coming into a passcode. The display screen recording is initiated by a management server sending instructions similar to start_v, start_i, or start_a. The researchers defined:

When Mandrake receives a start_v command, the service begins and masses the required URL in an application-owned webview with a customized JavaScript interface, which the applying makes use of to control the online web page it masses.

Whereas the web page is loading, the applying establishes a websocket connection and begins taking screenshots of the web page at common intervals, whereas encoding them to base64 strings and sending these to the C2 server. The attackers can use further instructions to regulate the body fee and high quality. The risk actors name this “vnc_stream”. On the identical time, the C2 server can ship again management instructions that make utility execute actions, similar to swipe to a given coordinate, change the webview measurement and backbone, change between the desktop and cellular web page show modes, allow or disable JavaScript execution, change the Consumer Agent, import or export cookies, return and ahead, refresh the loaded web page, zoom the loaded web page and so forth.

When Mandrake receives a start_i command, it masses a URL in a webview, however as a substitute of initiating a “VNC” stream, the C2 server begins recording the display screen and saving the file to a file. The recording course of is just like the “VNC” state of affairs, however screenshots are saved to a video file. Additionally on this mode, the applying waits till the consumer enters their credentials on the internet web page after which collects cookies from the webview.

The start_a command permits operating automated actions within the context of the present web page, similar to swipe, click on, and many others. If that is so, Mandrake downloads automation eventualities from the URL specified within the command choices. On this mode, the display screen can be recorded.

Display recordings may be uploaded to the C2 with the upload_i or upload_d instructions.

Neither Kaspersky nor Bitdefender supplied attribution for the group or what its motives are for spreading a adware and credential-stealing app as subtle as Mandrake. The apps Kaspersky found seem within the desk under. Google has since eliminated them from Play. Further indicators of compromise may be discovered within the Kaspersky publish.