Description
Certificate Transparency (CT) is an experimental IETF standard. The goal of it was to allow the public to audit which certificates were created by Certificate Authorities (CA). TLS has a weakness that comes from the large list of CAs that your browser implicitly trusts. If any of those CAs were to maliciously create a new certificate for a domain, your browser would trust it. CT adds benefits to TLS certificate trust: Companies can monitor who is creating certificates for the domains they own. It also allows browsers to verify that the certificate for a given domain is in the public log record.
These logs end up being a gold mine of information for penetration testers and red teams.