Sinclair Broadcast Group Inc. shares /zigman2/quotes/208678879/composite SBGI -1.49% slid 1.5% in premarket trade Monday, after the operator of TV stations said it is investigating a potential cybersecurity incident. The Baltimore, Md.-based Sinclair said it has identified that certain servers and workstations were encrypted with ransomware and that some of its networks were disrupted and data was taken. The company is working to determine what information the taken data contained and will take actions as appropriate. "Promptly upon detection of the security event, senior management was notified, and the company implemented its incident response plan, took measures to contain the incident, and launched an investigation," the company said in a statement. "Legal counsel, a cybersecurity forensic firm, and other incident response professionals were engaged. The Company also notified law enforcement and other governmental agencies." For now, the company said the incident has disrupted parts of its business, including the provision of local ads to local broadcast stations on behalf of clients. It is working to restore operations. It's too early to say if the incident will have a material impact on financial results. Shares are down 15% in the year to date, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +1.32% has gained 19%.