Adversaries may install SSL/TLS certificates that can be used during targeting. SSL/TLS certificates are files that can be installed on servers to enable secure communications between systems. Digital certificates include information about the key, information about its owner's identity, and the digital signature of an entity that has verified the certificate's contents are correct. If the signature is valid, and the person examining the certificate trusts the signer, then they know they can use that key to communicate securely with its owner. Certificates can be uploaded to a server, then the server can be configured to use the certificate to enable encrypted communication with it.
Adversaries may install SSL/TLS certificates that can be used to further their operations, such as encrypting C2 traffic (ex: Asymmetric Cryptography with Web Protocols) or lending credibility to a credential harvesting site. Installation of digital certificates may take place for a number of server types, including web servers and email servers.
Adversaries can obtain digital certificates (see Digital Certificates) or create self-signed certificates (see Digital Certificates). Digital certificates can then be installed on adversary controlled infrastructure that may have been acquired (Acquire Infrastructure) or previously compromised (Compromise Infrastructure).
This technique cannot be easily mitigated with preventive controls since it is based on behaviors performed outside of the scope of enterprise defenses and controls.
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Consider use of services that may aid in the tracking of certificates in use on sites across the Internet. In some cases it may be possible to pivot on known pieces of certificate information to uncover other adversary infrastructure.