A cyberattack on the Tribune Publishing Company's computer system led to printing and distribution problems at major newspapers. Newspapers affected included the Chicago Tribune, the Baltimore Sun and the San Diego Union-Tribune and the Los Angeles Times, both of which are no longer owned by Tribune Publishing but still share some systems.

Jeff Light, the editor and publisher of the San Diego Union-Tribune, said in a statement the attack appeared to begin Thursday night and continued into Friday. Director of distribution Joe Robidoux said print subscribers should get Saturday's paper delivered with Sunday's edition.

The news of the cyberattack was first reported by the Los Angeles Times. A source told the Times the source of the attack was a "foreign entity."

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A spokesman for the Department of Homeland Security told Reuters they are investigating the attack.

According to a statement from Marisa Kollias, a spokeswoman for Tribune Publishing Company, the company's computer alert systems detected the presence of malware that impacted some back-office systems which are primarily used to publish and produce the newspapers.

"Every market across the company was impacted," Kollias told the Times.

The company worked to come up with a workaround to produce the newspapers, but there were some delays in delivery. Distribution was also affected of other newspapers, including The New York Times and the Wall Street Journal, that use the same printing presses in some markets as Tribune Publishing.

Kollias said there is no evidence customers' personally identifiable information or credit card had been impacted, nor was the information of subscribers, advertisers and online users.