The attack is being investigated by federal law enforcement, one of the sources said.
Multiple systems are still down this week, including access to the digital video library, according to employees from two stations. Weather computers were also not working for at least two stations.
Some station employees tell CNN they have not yet recovered email and are working on workarounds. Stations have asked staff not to open email on their phones. One station on Wednesday was experiencing new issues, including phone lines and broadcast software failing, an employee said.
Cox Media Group and its parent company have not commented publicly about the attack nor has any official statement come from corporate to staff.
Cox has 33 television stations in 20 markets across the US. Cox and Apollo Global Management, which owns Cox, have not responded to CNN’s repeated requests for comment.
There has been nothing that’s been posted on ransomware extortion sites and no claims of responsibility, said Allan Liska of Recorded Future. Liska said if internal systems are affected that likely indicates ransomware.
Last week, after complaints about a change in programming, Hulu said on Twitter that there was “an issue with the feed” from one of the Cox stations.
“Apologies for the trouble! There’s currently an issue with the feed from WSB that’s under investigation, and we hope to see this cleared up soon. We appreciate your patience in the meantime!,” the June 3 tweet read.
This story is breaking and will be updated.