A penetration test has demonstrated that domain administrator accounts were vulnerable to pass-the-hash attacks. Which of the following would have been the best strategy to prevent the threat actor from using domain administrator accounts?

Implementing a Privileged Access Management (PAM) solution is the best strategy because it specifically addresses the security of privileged accounts, like domain administrators, by controlling, monitoring, and auditing their access. PAM solutions can enforce strong authentication, just-in-time access, and session recording, significantly reducing the attack surface for pass-the-hash and other credential theft attacks. Auditing accounts for password compliance is good practice but doesn't prevent pass-the-hash if the hash is compromised. Creating IDS policies monitors access but is a reactive measure; it doesn't prevent the attack. Enforcing password expiration is also a good general security practice but doesn't directly mitigate pass-the-hash vulnerabilities, as the hash can still be used even if the password has expired or is soon to expire.