A hacker has gained access to a database containing names, job titles, email addresses, and phone numbers of tens of thousands of government workers.
The data contains details on as many as 20,000 FBI employees and 9,000 Homeland Security employees.
Motherboard first received word of the hack on Sunday morning, along with access to the database of information. The publication was able to verify some of the details authenticity of the leaked data.
On Sunday, a Twitter account with a pro-Palestinian agenda reportedly published some data, and included a screenshot of the FBI computer the hacker allegedly gained access to.
On Monday, he made good on a promise to release the rest of the information.
The hacker did not tell Motherboard how sensitive the data is, but noted that the attack was carried out by compromising the email account of a Justice Department employee.
"We are looking into the reports of purported disclosure of DHS employee contact information," a DHS spokesperson said in a statement. "We take these reports very seriously, however there is no indication at this time that there is any breach of sensitive or personally identifiable information."
In January, the Fraternal Order of Police (FOP), a union representing law enforcement in the US, said it believed 2.5GB of data was taken from its servers and dumped online.
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We have reached out to the DHS and FBI for more details on the alleged hack.
This article has been updated with additional information.