LONDON (BLOOMBERG) - Professional criminals holding businesses to ransom - often with the support of nation-states - is the key online threat facing the Britain, the country's cyber security chief will say on Monday (June 14).

Ms Lindy Cameron, who is chief executive of the National Cyber Security Centre (NCSC), part of the spy agency GCHQ, or Government Communications Headquarters, will warn the market that ransomware has become increasingly "professional".

Some criminals even offer 24/7 call centres "to quickly pay the ransom and get yourself back online" or offering to research businesses' "insurance policy to see if you are covered to pay ransoms", she will say, according to her office.

"These criminals don't exist in a vacuum," Ms Cameron will say in a lecture to the Royal United Services Institute (RUSI) in London. "They are often enabled and facilitated by states acting with impunity."

On Sunday, the Group of Seven used its final communique to call on Russia "to identify, disrupt, and hold to account those within its borders who conduct ransomware attacks, abuse virtual currency to launder ransoms, and other cyber crimes".

In a speech in March, Ms Cameron said Russia "poses the most acute and immediate threat" to Britain, but China's size, scale and technological ambition is also being watched. Britain also frequently cites North Korea and Iran as security threats.

Ms Cameron will also reveal that it's "almost certain" that the primary cyber threat to think-tanks - such as RUSI, where she is speaking - in Britain is from nation-state espionage groups.

They are "highly likely" seeking to "gain strategic insights into government policy, trade agreements and commercially sensitive information", according to a recent NCSC assessment.