Code signing provides a level of authenticity on a binary from the developer and a guarantee that the binary has not been tampered with.  However, adversaries are known to use code signing certificates to masquerade malware and tools as legitimate binaries . The certificates used during an operation may be created, forged, or stolen by the adversary.  
Code signing to verify software on first run can be used on modern Windows and macOS/OS X systems. It is not used on Linux due to the decentralized nature of the platform. 
Code signing certificates may be used to bypass security policies that require signed code to execute on a system.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Darkhotel has used code-signing certificates on its malware that are either forged due to weak keys or stolen. Darkhotel has also stolen certificates and signed backdoors and downloaders with them.
FIN7 has signed Carbanak payloads with legally purchased code signing certificates. FIN7 has also digitally signed their phishing documents, backdoors and other staging tools to bypass security controls.
Collect and analyze signing certificate metadata on software that executes within the environment to look for unusual certificate characteristics and outliers.
- Wikipedia. (2015, November 10). Code Signing. Retrieved March 31, 2016.
- Thomas. (2013, July 15). New signed malware called Janicab. Retrieved July 17, 2017.
- Ladikov, A. (2015, January 29). Why You Shouldn’t Completely Trust Files Signed with Digital Certificates. Retrieved March 31, 2016.
- Shinotsuka, H. (2013, February 22). How Attackers Steal Private Keys from Digital Certificates. Retrieved March 31, 2016.
- Raiu, C., and Ivanov, A. (2016, June 17). Operation Daybreak. Retrieved February 15, 2018.
- Lunghi, D., et al. (2017, December). Untangling the Patchwork Cyberespionage Group. Retrieved July 10, 2018.
- Miller-Osborn, J. and Grunzweig, J.. (2017, February 16). menuPass Returns with New Malware and New Attacks Against Japanese Academics and Organizations. Retrieved March 1, 2017.
- Nakamura, Y.. (2017, February 17). ChChes - Malware that Communicates with C&C Servers Using Cookie Headers. Retrieved March 1, 2017.
- PwC and BAE Systems. (2017, April). Operation Cloud Hopper: Technical Annex. Retrieved April 13, 2017.
- ClearSky Cyber Security and Trend Micro. (2017, July). Operation Wilted Tulip: Exposing a cyber espionage apparatus. Retrieved August 21, 2017.
- Kaspersky Lab's Global Research and Analysis Team. (2014, November). The Darkhotel APT A Story of Unusual Hospitality. Retrieved November 12, 2014.
- Kaspersky Lab's Global Research & Analysis Team. (2015, August 10). Darkhotel's attacks in 2015. Retrieved November 2, 2018.
- DiMaggio, J. (2016, April 28). Tick cyberespionage group zeros in on Japan. Retrieved July 16, 2018.
- M.Léveillé, M.. (2014, February 21). An In-depth Analysis of Linux/Ebury. Retrieved April 19, 2019.
- Kaspersky Lab's Global Research and Analysis Team. (2014, August 7). The Epic Turla Operation: Solving some of the mysteries of Snake/Uroburos. Retrieved December 11, 2014.
- Bennett, J., Vengerik, B. (2017, June 12). Behind the CARBANAK Backdoor. Retrieved June 11, 2018.
- Carr, N., et al. (2018, August 01). On the Hunt for FIN7: Pursuing an Enigmatic and Evasive Global Criminal Operation. Retrieved August 23, 2018.
- ESET. (2017, August). Gazing at Gazer: Turla’s new second stage backdoor. Retrieved September 14, 2017.
- Kaspersky Lab's Global Research & Analysis Team. (2017, August 30). Introducing WhiteBear. Retrieved September 21, 2017.
- Cherepanov, A. (2018, October). GREYENERGY A successor to BlackEnergy. Retrieved November 15, 2018.
- ClearSky Cybersecurity. (2017, January 5). Iranian Threat Agent OilRig Delivers Digitally Signed Malware, Impersonates University of Oxford. Retrieved May 3, 2017.
- Sherstobitoff, R. (2018, March 02). McAfee Uncovers Operation Honeybee, a Malicious Document Campaign Targeting Humanitarian Aid Groups. Retrieved May 16, 2018.
- FireEye. (2018, March 16). Suspected Chinese Cyber Espionage Group (TEMP.Periscope) Targeting U.S. Engineering and Maritime Industries. Retrieved April 11, 2018.
- Plan, F., et all. (2019, March 4). APT40: Examining a China-Nexus Espionage Actor. Retrieved March 18, 2019.
- Greenberg, A. (2019, March 25). A Guide to LockerGoga, the Ransomware Crippling Industrial Firms. Retrieved July 17, 2019.
- Villeneuve, N., Haq, H., Moran, N. (2013, August 23). OPERATION MOLERATS: MIDDLE EAST CYBER ATTACKS USING POISON IVY. Retrieved April 1, 2016.
- Ladley, F. (2012, May 15). Backdoor.Nerex. Retrieved February 23, 2018.
- McAfee. (2015, March 2). Netwire RAT Behind Recent Targeted Attacks. Retrieved February 15, 2018.
- Meltzer, M, et al. (2018, June 07). Patchwork APT Group Targets US Think Tanks. Retrieved July 16, 2018.
- Kaspersky Lab's Global Research and Analysis Team. (2014, November 24). THE REGIN PLATFORM NATION-STATE OWNAGE OF GSM NETWORKS. Retrieved December 1, 2014.
- Faou, M. and Boutin, J.. (2017, February). Read The Manual: A Guide to the RTM Banking Trojan. Retrieved March 9, 2017.
- Russinovich, M. (2016, July 4). SDelete v2.0. Retrieved February 8, 2018.
- DiMaggio, J.. (2016, March 15). Suckfly: Revealing the secret life of your code signing certificates. Retrieved August 3, 2016.
- Salem, E. (2019, April 25). Threat Actor TA505 Targets Financial Enterprises Using LOLBins and a New Backdoor Malware. Retrieved May 28, 2019.
- Vilkomir-Preisman, S. (2019, April 2). New ServHelper Variant Employs Excel 4.0 Macro to Drop Signed Payload. Retrieved May 28, 2019.
- Kaspersky Lab's Global Research and Analysis Team. (2013, April 11). Winnti. More than just a game. Retrieved February 8, 2017.