Adversaries may search public digital certificate data for information about victims that can be used during targeting. Digital certificates are issued by a certificate authority (CA) in order to cryptographically verify the origin of signed content. These certificates, such as those used for encrypted web traffic (HTTPS SSL/TLS communications), contain information about the registered organization such as name and location.
Adversaries may search digital certificate data to gather actionable information. Threat actors can use online resources and lookup tools to harvest information about certificates. Digital certificate data may also be available from artifacts signed by the organization (ex: certificates used from encrypted web traffic are served with content). Information from these sources may reveal opportunities for other forms of reconnaissance (ex: Active Scanning or Phishing for Information), establishing operational resources (ex: Develop Capabilities or Obtain Capabilities), and/or initial access (ex: External Remote Services or Trusted Relationship).
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. Efforts should focus on minimizing the amount and sensitivity of data available to external parties.
Much of this activity may have a very high occurrence and associated false positive rate, as well as potentially taking place outside the visibility of the target organization, making detection difficult for defenders.
Detection efforts may be focused on related stages of the adversary lifecycle, such as during Initial Access.