The cyber outfit, which calls itself ISIS Hacking Division, made the claim as it published a "hit list" of people it alleged were US drone pilots, according to a report by the Sunday Times.
In spite of the credibility of the targets, the data appeared to have been gleaned through online sources available to the public, rather than through compromised security.
"In our next leak we may even disclose secret intelligence the ISIS has just received from a source the brothers in the UK have spent some time acquiring from the Ministry of Defense in London as we slowly and secretly infiltrate England and the USA online and off,” the hacker group wrote.
The ministry declined to enlarge on what personnel security measures it is taking for its staff.
“While we don’t comment on cyber threats, Britain is a world leader in cyber security and we are investing more than ever before in the UK’s capabilities to protect our national interest,” said a ministry spokesman. “Our increasing defense budget means that we can stay ahead of our adversaries in cyberspace while also investing in conventional capabilities.”
The target list the group has released includes names, photographs and other biographical details of the people it claimed were US Air Force staff members involved in drone operations.
“These 75 crusaders are posted as targets for our brothers and sisters in America and worldwide to hunt down and kill,” a message said. "Kill them wherever they are, knock on their doors and behead them, stab them, shoot them in the face or bomb them."
On Friday, another ISIS-linked group of hackers posted a list of thousands of people living in New York and asked the followers of the Takfiri group to target them.
The list contains the names, home addresses and email addresses of some 3,000 New Yorkers, but some of the data is apparently outdated.
The data also includes private information of some employees with the US State Department and Homeland Security.
Daesh (ISIS / ISIL) terrorists, who were initially trained by the CIA in Jordan in 2012 to destabilize the Syrian government, now control large parts of Iraq and Syria.
The group has conducted terrorist attacks in some other countries, including France and Belgium.
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