Cellcom Outage Mobile Carrier Suffers Major Cyberattack

Wisconsin-based wireless carrier Cellcom suffered a major cyberattack that severely disrupted mobile services for nearly 75,000 subscribers across Northeast Wisconsin and Michigan’s Upper Peninsula. The outage began on May 14, leaving customers unable to make calls, send SMS messages, or port numbers, though 911 services, mobile data, iMessage, and RCS messaging continued to function.
At first, Cellcom described the disruption as a technical malfunction, but on May 20, CEO Brighid Riordan formally confirmed that it was caused by a cyber incident. The company stressed there was no evidence of sensitive customer data being compromised, since the affected systems did not store personal or financial information.
Investigations suggested that the attack involved multi-vector DDoS tactics, peaking at nearly 4.8 million requests per second, overwhelming the network with volumetric flooding and TCP-state exhaustion methods. Cellcom worked with cybersecurity experts and notified law enforcement while technicians labored around the clock to restore service.