Cisco Duo warns third-party data breach exposed SMS MFA logs. Cisco Duo’s security team warns that hackers stole some customers’ VoIP and SMS logs for multi-factor authentication (MFA) messages in a cyberattack on their telephony provider. Cisco Duo is a multi-factor authentication and Single Sign-On service used by corporations to provide secure access to internal networks and corporate applications. Duo’s homepage reports that it serves 100,000 customers and handles over a billion authentications monthly, with over 10,000,000 downloads on Google Play. Third-party company: Unknown Telephony Provider.