Largest North American Steel Producer Nucor Partially Halts Production Following Cyberattack

Charlotte, NC - May 2025 - Nucor Corporation, North America's largest steel producer, recently suffered a significant cybersecurity incident that forced the company to take some of its IT systems offline and temporarily halt production at various facilities. The breach, detected around May 13-14, 2025, involved unauthorized third-party access to the company's information technology infrastructure.

This attack comes at a particularly inopportune time, as Nucor had been signaling strong performance. Just weeks prior, CEO Leon Topalian had spoken to CNBC about the company's positive outlook, stating it had "the largest backlog in the history of our company, ever.”

In response to the intrusion, Nucor activated its incident response plan, which included proactively shutting down potentially affected systems to contain the threat. The company also engaged leading external cybersecurity experts to assist in the investigation and has notified federal lawenforcement agencies.

While the full scope and specific nature of the attack-including whether data was exfiltrated or if it was a ransomware incident-have not yet been publicly detailed, the disruption was significant enough to warrant a temporary cessation of operations at multiple locations across its North American footprint, which includes facilities in the United States, Canada, and Mexico. Nucor stated it was in the process of restarting affected operations.

The company, a key player in supplying steel for construction, automotive, and other critical sectors, disclosed the incident in a Form 8-K filing with the U.S. Securities and Exchange Commission (SEC). As of the initial reports, no specific threat actor or group have as-of-yet publicly claimed responsibility for the cyberattack.