A cyber attack targeting US newspapers delayed the distribution of titles such as The Los Angeles Times and the Chicago Tribune, among others. West Coast editions of the Wall Street Journal and the New York Times were also delayed.
The attack meant journalists across southern California couldn't send completed pages to printers as deadlines loomed.
Tribune Publishing, the affected company, said it first detected the malware on Friday and quickly tried to quarantine and restore server operations. The security patches that were made didn't hold and the virus began to reinfect the network.
"We believe the intention of the attack was to disable infrastructure, more specifically servers, as opposed to looking to steal information," said an anonymous source with knowledge of the attack, according to the LA Times.
In a statement Saturday, Tribune Publishing said that the personal data of subscribers, online users, and advertising clients had not been accessed. "We apologise for any inconvenience and thank our readers and advertising partners for their patience as we investigate the situation."
The attack is believed to have been launched from outside the US but it's unknown as to whether the attacker is a nation-state or another type of entity, a source told the LA Times.
"Every market across the company was impacted," said Marisa Kollias, spokeswoman for Tribune Publishing, which declined to provide specific information about the attack. The virus affected back-office systems used to publish and produce newspapers.
LA Times workers were reportedly preparing to hand-deliver pages from its El Segundo offices to its Olympic printing plant in downtown LA in order to meet distribution deadlines.
San Diego publications were hit particularly hard by the cyber attack, between 85% and 90% of the Saturday edition of the Union-Tribune did not reach subscribers on Saturday morning, said Jeff Light, publisher and editor of the San Diego Union-Tribune.
"Papers that should have arrived in San Diego around 3-4 am. instead arrived at 7 am and 8 am." Light said. Because the newspaper relies on independent contractors to deliver the paper to neighbourhoods, many of those people were not available later in the day to do the deliveries.
The LA Times was affected by the delays but most of its subscribers got their papers on Saturday morning, just a few hours later than usual.
