While most of America settled down to enjoy the Super Bowl on Sunday a cyber-criminal carried out the first of two threats and published a list of the names of 9,000 Department of Homeland Security officers. This was followed on Monday by the publication of a list of the names of 20,000 FBI officers.
The hacker included the hashtag #FreePalestine in tweets.
US tech publication Motherboard received a list of names, email addresses, phone numbers and job descriptions and was able to validate names listed by contacting the numbers on the list.
The US Department of Justice says it is examining the breach.
“This unauthorised access is still under investigation; however, there is no indication at this time that there is any breach of sensitive personally identifiable information,” the US Department of Justice stated.
It is understood that the intruder impersonated a government employee and then used that information to gain access to other parts of the system.
It is likely the intruder gained information through a phishing attack.
The episode is the latest in a string of high-profile cyberattacks that have rocked America.
The attack is reminiscent of a spate of attacks last year that saw the emails of the Homeland Security secretary Jeh Johnson and the director of the CIA John Brennan exposed.
Months earlier, Chinese hackers were believed to have been behind a major attack that exposed sensitive information belonging to millions of US government workers.
There was also the attack on Anthem that saw customers past and present have their information stolen.
In May last year, it also emerged that hackers attacked the IRS and may have gotten away with more than $50m.