New LokiBot-Linked Android Trojan Emerges
15.6.18 securityweek Android

A newly discovered banking Trojan targeting Android 7 and 8 versions is using the same command and control (C&C) server as LokiBot, Threat Fabric (formerly known as SfyLabs) reports.

Dubbed MysteryBot, the new threat appears to be either an update for LokiBot or a brand new malware family from the same threat actor. It features improved commands compared to LokiBot, a new name, and modified network communication.

Although featuring generic Android banking Trojan functionalities, the new malware stands out in the crowd, courtesy of novel overlay, keylogging, and ransomware capabilities, researchers discovered.

The list of supported commands includes: call a given phone number, fetch contact list information, forward calls, copy all SMS messages, log keystrokes, encrypt files on external storage and delete all contacts, send an SMS message to all contacts, change default SMS app, call a USSD number, delete all SMS messages, and send SMS messages.

In addition to these capabilities, the Trojan can overlay phishing pages on top of legitimate applications, and uses a novel technique for that, to ensure success on Android 7 and 8 devices as well.

Restrictions in Security-Enhanced Linux (SELinux) and other security controls in new Android versions were meant to prevent malware from displaying fake windows over legitimate apps. The new technique leverages the Android PACKAGE_USAGE_STATS permission (Usage Access permission) to bypass the restrictions, and also abuses the AccessibilityService to get the permission.

Posing as an Adobe Flash Player app, the malware asks the victim to grant it the Usage Access permission, which enables its nefarious capabilities. The malware then attempts to monitor package names of the applications in the foreground. It targets over 100 applications with the overlays, including mobile banking and social platform apps.

MysteryBot also uses a new method of logging keystrokes: it calculates the location of the keys on the screen (it considers that each key has a set location on the screen), and places a different View over each of them (width and height of 0 pixels), which allows it to register which keys have been pressed.

The code, however, appears to be under development, as the malware doesn’t yet include the capability to send the logged keystrokes to the C&C server.

The malware also includes locker/ransomware capabilities, which are managed from a separate dashboard than the Trojan, the researchers reveal. MysteryBot can encrypt individually each file in the External Storage directory, and then delete the original files.

The malware places each file in a password-protected ZIP archive, but uses the same password for all archives (the key is generated during runtime). When completing the encryption, the malware displays a dialogue claiming the victim watched pornographic material and instructing them to contact the attacker via email.

The security researchers discovered that the passwords the malware uses are only 8 characters long, and that only characters of the Latin alphabet (upper and lower case) combined with numbers are used. Moreover, the IDs assigned to each victim can only be a number between 0 and 9,999, meaning that the same ID could actually be assigned to multiple victims.

“Although certain Android banking malware families such as but not limited to ExoBot 2.5, Anubis II, DiseaseBot have been exploring new techniques to perform overlay attacks on Android 7 and 8, it seems that the actor(s) behind MysteryBot have successfully implemented a workaround solution and have spent some time on innovation,” Threat Fabric concludes.