Authorities are trying to determine who disrupted phone and computer services in the Triangle over the weekend.
The State Bureau of Investigation is looking for the source of a cyber attack in Durham and Durham County.
Local officials said in a joint statement that phone calls to the city's services were temporarily shut down after the attack was detected.
Those systems are still being recovered but were expected to resume again. Critical public safety services remained in operation.
Authorities didn't say whether the hackers demanded a ransom.