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The Justice Department said Monday it is investigating how someone was able to sneak into one of the agency's computer systems and take thousands of federal workers' names, phone numbers, and email addresses and make them public this weekend.

The computer breach appears to have occurred in the Justice Department's Civil Division, where hackers apparently were able to trick an employee into providing enough information to enter the nonclassified computer network for that part of the department, according to officials familiar with the matter.

Security experts refer to this type of breach as "social engineering" as opposed to hacking, because they occur when a perpetrator tricks someone into sharing a critical piece of information, such as a password, rather than writing or using computer code to access a network.

On Sunday, a Twitter account posted a link to a list of contact information for roughly 9,000 employees of the Department of Homeland Security. On Monday afternoon, the same twitter account posted a link to a list of an estimated 20,000 FBI employees.

The lists amount to sections of the agencies' phone book -- with name, job title, phone number, and email listed for the individuals.

"There is no indication at this time that there is any breach of sensitive personally identifiable information," said a Justice Department spokesman. "The department takes this very seriously and is continuing to deploy protection and defensive measures to safeguard information. Any activity that is determined to be criminal in nature will be referred to law enforcement for investigation."

A DHS spokesman said the department is looking into the reported breach.

The breach is similar to a number of recent incidents in which the personal email accounts of senior government officials were compromised. Such incidents have revealed some information officials would rather not have in the public arena, but officials view them as more embarrassing than threatening because sensitive government secrets weren't exposed.

Nathan Catura, president of the Federal Law Enforcement Officers Association said the hacking of federal agencies "has evolved from a troubling matter to a lethal threat," and criticized the government for what he called a "leisurely reaction to these cyber incidents." Mr. Catura said such incidents could help terrorists or criminals identify and target government personnel in sensitive positions.

Write to Devlin Barrett at devlin.barrett@wsj.com

(END) Dow Jones Newswires

February 08, 2016 19:35 ET (00:35 GMT)

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