MFA is the most effective long-term control among the options because it directly reduces the attacker’s ability to succeed even when passwords are guessed, reused, or stolen. Brute-force and credential stuffing attacks exploit the single-factor nature of passwords; MFA adds an additional verification factor (authenticator app prompt, FIDO2 key, certificate-based auth), making account takeover significantly harder. From a containment standpoint, blocking IPs and enabling lockout can reduce immediate attack volume, but attackers commonly rotate IPs, use botnets, or target many accounts in parallel, which can also cause operational impact via account lockouts (denial of service against users). Cross-verifying false positives is important for accuracy, but it does not strengthen security. Notifying users can help awareness but is not a technical control. In SOC operations, the best practice is layered containment: immediate throttling/blocks and lockout tuning for the active attack, followed by durable hardening controls. MFA is the durable hardening step that meaningfully reduces future brute-force success rates and complements conditional access policies (geo/time/device risk) and stronger password protections.