Teams had tried to quarantine the malware, but it apparently "reinfected" systems linked to news production and printing.

The attack didn't compromise any subscribers, internet users or advertisers, Tribune said. The company acknowledged that "every market across the company" fell prey to the malware. People who didn't get their Saturday newspapers will receive it alongside the Sunday edition.

Tribune hasn't publicly identified a culprit, but an LA Times source said the malware came from outside the US. It wasn't clear if this was the work of criminals, state-backed attackers or someone else. However, evidence suggested that it might have been a form of Ryuk ransomware that tends to be deliberate. If so, this might have been an extortion attempt similar to those that were all too commonplace in 2018.