|Platform||Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows XP, Windows 7, Windows 8, Windows Server 2003 R2, Windows Server 2008 R2, Windows Server 2012 R2, Windows Vista, Windows 8.1|
|Data Sources||Process use of network, Process monitoring, Loaded DLLs|
|Defense Bypassed||Anti-virus, Process whitelisting|
Programs may specify DLLs that are loaded at runtime. Programs that improperly or vaguely specify a required DLL may be open to a vulnerability in which an unintended DLL is loaded. Side-loading vulnerabilities specifically occur when Windows Side-by-Side (WinSxS) manifests1 are not explicit enough about characteristics of the DLL to be loaded. Adversaries may take advantage of a legitimate program that is vulnerable to side-loading to load a malicious DLL.2
Adversaries likely use this technique as a means of masking actions they perform under a legitimate, trusted system or software process.
- Threat Group-3390 actors use DLL side-loading. Actors have used legitimate Kaspersky anti-virus variants in which the DLL acts as a stub loader that loads and executes the shell code.3
- PlugX is known to use DLL side-loading to evade anti-virus and to maintain persistence on a victim.243
- HTTPBrowser has used DLL side-loading.3
- OwaAuth has been loaded onto Exchange servers and disguised as an ISAPI filter (DLL file). The IIS w3wp.exe process then loads the malicious DLL.3
- Sakula uses DLL side-loading, typically using a digitally signed sample of Kaspersky Anti-Virus (AV) 6.0 for Windows Workstations or McAfee's Outlook Scan About Box to load malicious DLL files.5
- During the T9000 installation process, it drops a copy of the legitimate Microsoft binary igfxtray.exe. The executable contains a side-loading weakness which is used to load a portion of the malware.6
- DLL side-loading has been used to execute BBSRAT through a legitimate Citrix executable ssonsvr.exe which is vulnerable to the technique. The Citrix executable was dropped along with BBSRAT by the dropper.7
- BADNEWS typically loads its DLL file into a legitimate signed Java executable.8
Update software regularly. Install software in write-protected locations. Use the program sxstrace.exe that is included with Windows along with manual inspection to check manifest files for side-loading vulnerabilities in software.
Monitor processes for unusual activity (e.g., a process that does not use the network begins to do so). Track DLL metadata, such as a hash, and compare DLLs that are loaded at process execution time against previous executions to detect differences that do not correlate with patching or updates.
- Microsoft. (n.d.). Manifests. Retrieved June 3, 2016.
- Stewart, A. (2014). DLL SIDE-LOADING: A Thorn in the Side of the Anti-Virus Industry. Retrieved November 12, 2014.
- Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, August 5). Threat Group-3390 Targets Organizations for Cyberespionage. Retrieved January 25, 2016.
- Scott, M.. (2014, June 10). Clandestine Fox, Part Deux. Retrieved January 14, 2016.
- Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, July 30). Sakula Malware Family. Retrieved January 26, 2016.
- Grunzweig, J. and Miller-Osborn, J.. (2016, February 4). T9000: Advanced Modular Backdoor Uses Complex Anti-Analysis Techniques. Retrieved April 15, 2016.
- Lee, B. Grunzweig, J. (2015, December 22). BBSRAT Attacks Targeting Russian Organizations Linked to Roaming Tiger. Retrieved August 19, 2016.
- Settle, A., et al. (2016, August 8). MONSOON - Analysis Of An APT Campaign. Retrieved September 22, 2016.