New Android Trojan ‘SoumniBot’ Evades Detection with Clever Tricks

A new Android trojan identified as SoumniBot has been detected in the wild concentrating on buyers in South Korea by leveraging weaknesses in the manifest extraction and parsing course of action.

The malware is “noteworthy for an unconventional method to evading assessment and detection, namely obfuscation of the Android manifest,” Kaspersky researcher Dmitry Kalinin mentioned in a complex examination.

Each and every Android application comes with a manifest XML file (“AndroidManifest.xml”) which is found in the root directory and declares the numerous components of the application, as effectively as the permissions and the components and software program functions it demands.

Recognizing that threat hunters typically start their analysis by inspecting the app’s manifest file to figure out its habits, the danger actors powering the malware have been discovered to leverage three different techniques to resist examination.

The initial strategy includes the use of an invalid Compression system benefit when unpacking the APK’s manifest file applying the libziparchive library, which treats any benefit other than 0x0000 or 0x0008 as uncompressed.

“This allows application developers to put any worth other than 8 into the Compression approach and create uncompressed knowledge,” Kalinin stated.

“Although any unpacker that accurately implements compression strategy validation would take into account a manifest like that invalid, the Android APK parser acknowledges it appropriately and makes it possible for the application to be mounted.”

It can be well worth pointing out here that the process has been adopted by threat actors related with numerous Android banking trojans because April 2023.

Next, SoumniBot misrepresents the archived manifest file size, offering a benefit that exceeds the real figure, as a result of which the “uncompressed” file is specifically copied, with the manifest parser disregarding the rest of the “overlay” information that takes up the relaxation of the accessible place.

“Stricter manifest parsers wouldn’t be ready to examine a file like that, whilst the Android parser handles the invalid manifest without having any faults,” Kalinin claimed.

The remaining technique has to do with making use of lengthy XML namespace names in the manifest file, consequently earning it complicated for assessment applications to allocate plenty of memory to method them. That said, the manifest parser is created to overlook namespaces, and, as a consequence, no glitches are lifted when managing the file.

SoumniBot, after launched, requests its configuration information and facts from a challenging-coded server tackle to get the servers utilised to send the collected data and obtain instructions using the MQTT messaging protocol, respectively.

It is really built to start a malicious provider that restarts each and every 16 minutes if it terminates for some cause, and uploads the data each 15 seconds. This consists of unit metadata, speak to lists, SMS messages, pictures, films, and a record of set up applications.

The malware is also capable of adding and deleting contacts, sending SMS messages, toggling silent method, and enabling Android’s debug method, not to mention hiding the application icon to make it challenging to uninstall from the gadget.

One noteworthy function of SoumniBot is its skill to research the exterior storage media for .vital and .der information that contains paths to “/NPKI/yessign,” which refers to the digital signature certificate company available by South Korea for governments (GPKI), financial institutions, and on line stock exchanges (NPKI).

“These documents are digital certificates issued by Korean banking institutions to their clients and utilized for signing in to on the internet banking services or confirming banking transactions,” Kalinin mentioned. “This approach is very unheard of for Android banking malware.”

Before this calendar year, cybersecurity firm S2W exposed aspects of a malware campaign carried out by the North Korea-connected Kimusuky group that created use of a Golang-dependent details stealer called Troll Stealer to siphon GPKI certificates from Windows devices.

“Malware creators find to optimize the variety of devices they infect without staying observed,” Kalinin concluded. “This motivates them to seem for new ways of complicating detection. The builders of SoumniBot sadly succeeded owing to insufficiently stringent validations in the Android manifest parser code.”

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Some parts of this article are sourced from:
thehackernews.com