London: British intelligence has uncovered a sophisticated espionage operation of the Islamic State in which jihadists targeted email accounts of top ministers, including the Home Secretary, according to a media report.
An investigation by Government Communications Headquarters (GCHQ) has discovered that extremists linked to the Islamic State of Iraq and Syria (ISIS) have been targeting information held by some of Prime Minister David Cameron's most senior ministers, including Theresa May, The Telegraph reported.
At least one of the plot's ringleaders was killed by a drone strike in an operation disclosed by Cameron last week.
By hacking into the private offices of senior ministers, the extremists could have discovered events that government figures and members of the Royal family were expected to attend.
The recent cyber threat first emerged in a warning to Whitehall security officials in May and it is understood that the plans to attack Britain were exposed by the GCHQ investigation, the report said.
It is unclear what information the extremists were able to access, but it is understood that no security breaches occurred, it said.
However, officials were told to tighten security procedures, including changing passwords, the report said.
The British daily said it had learnt of the operation several months ago but agreed not to publish while the investigation continued.
It emerged last Monday that a British jihadist had been killed in Syria by the UK forces after he directed a plot to kill the Queen.
The Prime Minister said it was the first time Britain's forces had directed an attack against one of its own citizens while not at war.
Reyaad Khan, 21, an ISIS fighter from Cardiff, was killed by a drone operated from Lincolnshire.
A second Briton, Junaid Hussain, a computer hacker from Birmingham, was also killed by US forces three days after the British strike.
Hussain, who joined ISIS in 2013, with Sally Jones, 46, his Muslim convert wife, is thought to have been involved in the cyber attack.
The disclosure shows how the so-called "war on terror" has developed because of ISIS' cyber capabilities -- computer hackers are known to have been recruited by the group to "actively target the West".
At the beginning of this year, Twitter and YouTube accounts of the US Central Command (Centcom) were hacked by a group calling itself the "CyberCaliphate".