|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.
- APT3 has been known to side load DLLs with a valid version of Chrome with one of their tools. 3
- Threat Group-3390 actors have used 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.45
- menuPass has used DLL side-loading to launch versions of Mimikatz and PwDump6.6
- BADNEWS typically loads its DLL file into a legitimate signed Java executable.7
- 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.8
- HTTPBrowser has used DLL side-loading.4
- 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.4
- PlugX has used to use DLL side-loading to evade anti-virus and to maintain persistence on a victim.23469
- 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.10
- 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.11
- Wingbird side loads a malicious file, sspisrv.dll, in part of a spoofed lssas.exe service.1213
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.
- Scott, M.. (2014, June 10). Clandestine Fox, Part Deux. Retrieved January 14, 2016.
- Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, August 5). Threat Group-3390 Targets Organizations for Cyberespionage. Retrieved January 25, 2016.
- Counter Threat Unit Research Team. (2017, June 27). BRONZE UNION Cyberespionage Persists Despite Disclosures. Retrieved July 13, 2017.
- PwC and BAE Systems. (2017, April). Operation Cloud Hopper: Technical Annex. Retrieved April 13, 2017.
- Settle, A., et al. (2016, August 8). MONSOON - Analysis Of An APT Campaign. Retrieved September 22, 2016.
- Lee, B. Grunzweig, J. (2015, December 22). BBSRAT Attacks Targeting Russian Organizations Linked to Roaming Tiger. Retrieved August 19, 2016.
- Lancaster, T. and Idrizovic, E.. (2017, June 27). Paranoid PlugX. Retrieved July 13, 2017.
- 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.
- Anthe, C. et al. (2016, December 14). Microsoft Security Intelligence Report Volume 21. Retrieved November 27, 2017.
- Microsoft. (2017, November 9). Backdoor:Win32/Wingbird.A!dha. Retrieved November 27, 2017.