Mysterious family of malware hid in Google Play for years

A mysterious family of Android malware with a demonstrated historical past of successfully concealing its myriad spying actions has as soon as once more been discovered 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 family of extremely intrusive malware that safety agency Bitdefender referred to as out in 2020. Bitdefender mentioned the apps appeared in two waves, one in 2016 by way of 2017 and once more in 2018 by way of 2020. Mandrake’s skill to go unnoticed then was the consequence 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 closing payload solely to victims who had been extraordinarily narrowly focused
• Containing a kill change the builders named seppuku (Japanese kind of ritual suicide) that absolutely wiped all traces of the malware
• Fully practical decoy apps in classes together with finance, Auto & Vehicles, Video Players & Editors, Art & Design, and Productivity
• Quick fixes for bugs reported in feedback
• TLS certificates pinning to hide communications with command and management servers.

Lurking in the shadows

Bitdefender estimated the quantity of victims in the tens of 1000’s for the 2018 to 2020 wave and “most likely a whole bunch of 1000’s all through the total 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. Besides 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 determine and research malware, and fight malware protections launched in current years.

“The Mandrake spy ware 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 purposes of the primary marketing campaign stayed undetected for 4 years, the present marketing campaign lurked in the shadows for two years, whereas nonetheless out there for obtain on Google Play. This highlights the menace actors’ formidable expertise, and likewise that stricter controls for purposes earlier than being revealed in the markets solely translate into extra subtle, harder-to-detect threats sneaking into official app marketplaces.

A key function 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 determine malicious apps. All 5 of the apps Kaspersky found first appeared in Play in 2022 and remained out there for no less than a yr. The most up-to-date app was up to date on March 15 and faraway from the app market later that month. As of earlier this month, none of the apps had been detected as malicious by any main malware detection supplier.

One means of obfuscation was to maneuver malicious performance to native libraries, which had been obfuscated. Previously, Mandrake saved the malicious logic of the primary stage in what’s generally known as the applying DEX file, a sort of file that’s trivial to research. By switching the situation to the native library libopencv_dnn.so, the Mandrake code is more durable to research 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 had been much more stealthy.

The chief functions of Mandrake are to steal the person’s credentials and obtain and execute next-stage malicious purposes. But these actions are carried out solely in later-stage infections which are served solely to a small quantity of fastidiously chosen targets. The main technique 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 equivalent to start_v, start_i, or start_a. The researchers defined:

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

While 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 charge and high quality. The menace actors name this “vnc_stream”. At the identical time, the C2 server can ship again management instructions that make software execute actions, equivalent 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 User 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 an alternative 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 much like the “VNC” situation, however screenshots are saved to a video file. Also in this mode, the applying waits till the person enters their credentials on the internet web page after which collects cookies from the webview.

The start_a command permits working automated actions in the context of the present web page, equivalent to swipe, click on, and so on. If that is the case, Mandrake downloads automation eventualities from the URL specified in the command choices. In this mode, the display screen can be recorded.

Screen recordings might be uploaded to the C2 with the upload_i or upload_d instructions.

Neither Kaspersky nor Bitdefender offered attribution for the group or what its motives are for spreading a spy ware and credential-stealing app as subtle as Mandrake. The apps Kaspersky found seem in the desk under. Google has since eliminated them from Play. Additional indicators of compromise might be discovered in the Kaspersky put up.