Regsvr32
Regsvr32.exe is a command-line program used to register and unregister object linking and embedding controls, including dynamic link libraries (DLLs), on Windows systems. Regsvr32.exe can be used to execute arbitrary binaries. (Citation: Microsoft Regsvr32) Adversaries may take advantage of this functionality to proxy execution of code to avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of whitelists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe is also a Microsoft signed binary. Regsvr32.exe can also be used to specifically bypass process whitelisting using functionality to load COM scriptlets to execute DLLs under user permissions. Since regsvr32.exe is network and proxy aware, the scripts can be loaded by passing a uniform resource locator (URL) to file on an external Web server as an argument during invocation. This method makes no changes to the Registry as the COM object is not actually registered, only executed. (Citation: LOLBAS Regsvr32) This variation of the technique is often referred to as a "Squiblydoo" attack and has been used in campaigns targeting governments. (Citation: Carbon Black Squiblydoo Apr 2016) (Citation: FireEye Regsvr32 Targeting Mongolian Gov) Regsvr32.exe can also be leveraged to register a COM Object used to establish Persistence via Component Object Model Hijacking. (Citation: Carbon Black Squiblydoo Apr 2016)
Mitigations |
|
| Mitigation | Description |
|---|---|
| Regsvr32 Mitigation |
Microsoft's Enhanced Mitigation Experience Toolkit (EMET) Attack Surface Reduction (ASR) feature can be used to block regsvr32.exe from being used to bypass whitelisting. (Citation: Secure Host Baseline EMET) |
| Exploit Protection |
Deploy capabilities that detect, block, and mitigate conditions indicative of software exploits. These capabilities aim to prevent exploitation by addressing vulnerabilities, monitoring anomalous behaviors, and applying exploit-mitigation techniques to harden systems and software. Operating System Exploit Protections: - Use Case: Enable built-in exploit protection features provided by modern operating systems, such as Microsoft's Exploit Protection, which includes techniques like Data Execution Prevention (DEP), Address Space Layout Randomization (ASLR), and Control Flow Guard (CFG). - Implementation: Enforce DEP for all programs and enable ASLR to randomize memory addresses used by system and application processes. Windows: Configure Exploit Protection through the Windows Security app or deploy settings via Group Policy. `ExploitProtectionExportSettings.exe -path "exploit_settings.xml"` Linux: Use Kernel-level hardening features like SELinux, AppArmor, or GRSEC to enforce memory protections and prevent exploits. Third-Party Endpoint Security: - Use Case: Use endpoint protection tools with built-in exploit protection, such as enhanced memory protection, behavior monitoring, and real-time exploit detection. - Implementation: Deploy tools to detect and block exploitation attempts targeting unpatched software. Virtual Patching: - Use Case: Use tools to implement virtual patches that mitigate vulnerabilities in applications or operating systems until official patches are applied. - Implementation: Use Intrusion Prevention System (IPS) to block exploitation attempts on known vulnerabilities in outdated applications. Hardening Application Configurations: - Use Case: Disable risky application features that can be exploited, such as macros in Microsoft Office or JScript in Internet Explorer. - Implementation: Configure Microsoft Office Group Policies to disable execution of macros in downloaded files. |
Detection
Use process monitoring to monitor the execution and arguments of regsvr32.exe. Compare recent invocations of regsvr32.exe with prior history of known good arguments and loaded files to determine anomalous and potentially adversarial activity. Command arguments used before and after the regsvr32.exe invocation may also be useful in determining the origin and purpose of the script or DLL being loaded. (Citation: Carbon Black Squiblydoo Apr 2016)
References
- Microsoft. (2012, June 27). Using Software Restriction Policies and AppLocker Policies. Retrieved April 7, 2016.
- Corio, C., & Sayana, D. P. (2008, June). Application Lockdown with Software Restriction Policies. Retrieved November 18, 2014.
- NSA Information Assurance Directorate. (2014, August). Application Whitelisting Using Microsoft AppLocker. Retrieved March 31, 2016.
- Tomonaga, S. (2016, January 26). Windows Commands Abused by Attackers. Retrieved February 2, 2016.
- Gorzelany, A., Hall, J., Poggemeyer, L.. (2019, January 7). Windows Defender Application Control. Retrieved July 16, 2019.
- Beechey, J. (2010, December). Application Whitelisting: Panacea or Propaganda?. Retrieved November 18, 2014.
- National Security Agency. (2016, May 4). Secure Host Baseline EMET. Retrieved June 22, 2016.
- Anubhav, A., Kizhakkinan, D. (2017, February 22). Spear Phishing Techniques Used in Attacks Targeting the Mongolian Government. Retrieved February 24, 2017.
- Nolen, R. et al.. (2016, April 28). Threat Advisory: “Squiblydoo” Continues Trend of Attackers Using Native OS Tools to “Live off the Land”. Retrieved April 9, 2018.
- LOLBAS. (n.d.). Regsvr32.exe. Retrieved July 31, 2019.
- Microsoft. (2015, August 14). How to use the Regsvr32 tool and troubleshoot Regsvr32 error messages. Retrieved June 22, 2016.
Связанные риски
Каталоги
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