Cisco Duo's Multifactor Authentication Service Breached

A third-party telephony provider that handles SMS and VOIP for Cisco Duo was compromised via social engineering and stolen employee credentials; attackers downloaded SMS message logs for users between March 1 and March 31, 2024. The logs contained phone numbers, carriers, country/state, timestamps and other metadata (but not message content); Cisco has advised customers to notify affected users and remain vigilant for follow-on phishing attacks.