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.
|APT37||APT37 has signed its malware with an invalid digital certificates listed as “Tencent Technology (Shenzhen) Company Limited.” |
|APT41||APT41 leveraged code-signing certificates to sign malware when targeting both gaming and non-gaming organizations. |
|BADNEWS||BADNEWS is sometimes signed with an invalid Authenticode certificate in an apparent effort to make it look more legitimate. |
|BOOSTWRITE||BOOSTWRITE has been signed by a valid CA. |
|ChChes||ChChes samples were digitally signed with a certificate originally used by Hacking Team that was later leaked and subsequently revoked.   |
|CopyKittens||CopyKittens digitally signed an executable with a stolen certificate from legitimate company AI Squared. |
|Darkhotel||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.  |
|Daserf||Some Daserf samples were signed with a stolen digital certificate. |
|Ebury||Ebury has installed a self-signed RPM package mimicking the original system package on RPM based systems. |
|Epic||Turla has used valid digital certificates from Sysprint AG to sign its Epic dropper. |
|FIN6||FIN6 has used Comodo code-signing certificates. |
|FIN7||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.  |
|Gazer||Gazer versions are signed with various valid certificates; one was likely faked and issued by Comodo for "Solid Loop Ltd," and another was issued for "Ultimate Computer Support Ltd."  |
|GreyEnergy||GreyEnergy digitally signs the malware with a code-signing certificate. |
|Helminth||Helminth samples have been signed with legitimate, compromised code signing certificates owned by software company AI Squared. |
|Honeybee||Honeybee uses a dropper called MaoCheng that harvests a stolen digital signature from Adobe Systems. |
|Janicab||Janicab used a valid AppleDeveloperID to sign the code to get past security restrictions. |
|Leviathan||Leviathan has used stolen code signing certificates to sign malware.  |
|LockerGoga||LockerGoga has been signed with stolen certificates in order to make it look more legitimate. |
|Molerats||Molerats has used forged Microsoft code-signing certificates on malware. |
|More_eggs||More_eggs has used a signed binary shellcode loader and a signed Dynamic Link Library (DLL) to create a reverse shell. |
|Nerex||Nerex drops a signed Microsoft DLL to disk. |
|NETWIRE||The NETWIRE client has been signed by fake and invalid digital certificates. |
|QuasarRAT||A QuasarRAT .dll file is digitally signed by a certificate from AirVPN. |
|Regin||Regin stage 1 modules for 64-bit systems have been found to be signed with fake certificates masquerading as originating from Microsoft Corporation and Broadcom Corporation. |
|RTM||RTM samples have been signed with a code-signing certificates. |
|SDelete||SDelete is digitally signed by Microsoft. |
|Suckfly||Suckfly has used stolen certificates to sign its malware. |
|TA505||TA505 has signed payloads with code signing certificates from Thawte and Sectigo.  |
|Winnti Group||Winnti Group used stolen certificates to sign its malware. |
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Collect and analyze signing certificate metadata on software that executes within the environment to look for unusual certificate characteristics and outliers.
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