The novel, titled 'Dead Line' and published next week, stars a young intelligence officer called Liz Carlyle.
Her ex-boyfriend is a journalist who uncovers another reporter who has been helping a foreign intelligence service's - SCLB
The plot is set around a peace conference at Gleneagles in Scotland when Syrian Intelligence say they have heard of a plot to disrupt the meeting in a big way.
The portrayal of Mossad, the Israeli intelligence service, also plays a big part in the book.
"Fathoming motives in the Middle East is the equivalent of building sandcastles," says one MI5 officer in the book.
"You can erect the most impressive structure and then one big wave can wash it all away."
In the book the CIA characters say that the British "don't trust the Israelis".
Dame Rimington, 73, became the first woman director general of MI5 in 1992 and held the post until her retirement in 1996.
The novel is the fourth in the Liz Carlyle series.
MI5 tried to prevent her, on national security grounds, from publishing the memoirs, called "Open Secret".
At the time she said that in order to gain clearance for her book, she was forced to make changes.
These included removing any reference to Britain's elite SAS soldiers, even when she described their well-documented killings of three unarmed members of the Irish Republican Army in Gibraltar in 1988.
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