Ryuk ransomware is believed to be the culprit behind printing and delivery issues for “all Tribune Publishing newspapers” — as well as newspapers that used to be part of Tribune Publishing.

The malware was discovered and later quarantined on Friday, but the security patches failed to hold when the servers were brought back online and the ransomware began to re-infect the network and impact servers used for news production and manufacturing processes. A Tribune spokesperson said the malware “impacted some back-office systems, which are primarily used to publish and produce newspapers across our properties.”