Uncovering .NET Malware Obfuscated by Encryption and Virtualization

    Date: 03/04/2025

    Severity: High

    Summary

    This article explores obfuscation techniques in popular malware families and highlights opportunities for automating the unpacking process. We analyze observed samples, demonstrating how to extract configuration parameters by unpacking each stage. Automating this process would enable sandboxes performing static analysis to retrieve critical malware configuration data. Adversaries use techniques like code virtualization, staged payload delivery, dynamic code loading, AES encryption, and multi-stage payloads to distribute malware such as Agent Tesla, XWorm, and FormBook/XLoader.

    Indicators of Compromise (IOC) List 

    Domains\Urls :

    weidmachane.zapto.org

    IP Address : 

    66.63.168.133

    Hash : 

    a02bdd3db4dfede3d6d8db554a266bf9f87f4fa55ee6cde5cbe1ed77c514cdee
    
    3d8187853d481c74408d56759f427e2c3446e9310c2d109fd38a0f200696c32d
    
    098a18e96c4fb250ffadb3f01d601240c74a4d9f5df94cb72bd44cc81b80b2af
    
    695e038452a656d58471f284edb8d81754b78258a6afd3d8f62ae8a47c3130d9
    
    d72f4ef2e5caea42749d542384b6634e65e29f3aef5d09a9c231cc09e76e4988

    Gurucul Threat Detection and Incident Response (TDIR) Queries for Detection

    Domains\Urls :

    userdomainname like "weidmachane.zapto.org" or url like "weidmachane.zapto.org"

    IP Address :

    dstipaddress IN ("66.63.168.133") or ipaddress IN ("66.63.168.133") or publicipaddress IN ("66.63.168.133") or srcipaddress IN ("66.63.168.133")

    Hash : 

    sha256hash IN ("a02bdd3db4dfede3d6d8db554a266bf9f87f4fa55ee6cde5cbe1ed77c514cdee","3d8187853d481c74408d56759f427e2c3446e9310c2d109fd38a0f200696c32d","098a18e96c4fb250ffadb3f01d601240c74a4d9f5df94cb72bd44cc81b80b2af","695e038452a656d58471f284edb8d81754b78258a6afd3d8f62ae8a47c3130d9","d72f4ef2e5caea42749d542384b6634e65e29f3aef5d09a9c231cc09e76e4988")

    Reference:    

    https://unit42.paloaltonetworks.com/malware-obfuscation-techniques/


    Tags

    MalwareAgent TeslaXWormFormBookXloader

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