CompTIA Security+ Question K-31

A CA is compromised and attacks start distributing maliciously signed software updates. Which of the following can be used to warn users about the malicious activity?

A. Key escrow
B. Private key verification
C. Public key verification
D. Certificate revocation list

Answer: D

If we put the root certificate of the comprised CA in the CRL, users will know that this CA (and the certificates that it has issued) no longer can be trusted. The CRL (Certificate revocation list) is exactly what its name implies: a list of subscribers paired with digital certificate status. The list enumerates revoked certificates along with the reason(s) for revocation. The dates of certificate issue, and the entities that issued them, are also included. In addition, each list contains a proposed date for the next release.