Die Another Day

MI6 officer James Bondâagent 007âinfiltrates a North Korean military base, where Colonel Tan-Sun Moon is illegally trading weapons for African blood diamonds. After Moon's assistant Zao discovers that Bond is a British agent, Moon attempts to kill Bond and a hovercraft chase ensues, which ends with Moon's apparent death. Bond survives, but is captured by North Korean soldiers and imprisoned by the Colonel's father, General Moon.
After 14 months of captivity and torture, Bond is traded for Zao in a prisoner exchange. He is sedated and taken to meet M, who informs him that his status as a 00 Agent is suspended under suspicion of having leaked information under duress. Bond is convinced that he has been set up by a double agent in the British government and decides to avenge his betrayal. After escaping from the custody of MI6, he discovers that he is in Hong Kong, where he learns from a Chinese agent that Zao is in Cuba.
In Havana Bond meets NSA agent Giacinta 'Jinx' Johnson and follows her to a gene therapy clinic, where patients can have their appearances altered through DNA restructuring. Bond locates Zao inside the clinic and attempts to kill him, but Zao escapes. He leaves behind a pendant which leads Bond to a cache of diamonds, identified as conflict diamonds, but bearing the crest of the company owned by British billionaire Gustav Graves.
At Blades Club in London Bond meets Graves, along with his assistant Miranda Frost, who is also an undercover MI6 agent. After a fencing exercise (and a literal sword-fight), Bond is invited by Graves to Iceland for a scientific demonstration. Shortly afterwards, M restores Bond's Double-0 status and offers assistance in the investigation.
At his ice palace in Iceland Graves unveils a new orbital mirror satellite, "Icarus", which is able to focus solar energy on a small area and provide year-round sunshine for crop development. During the night, Jinx infiltrates Graves' command centre, but is captured by Graves and Zao. Bond rescues her and later discovers that Colonel Moon is still alive. Moon has used the gene therapy technology to change his appearance, assuming the identity of Gustav Graves.
Bond confronts Graves, but Frost arrives to reveal herself as the traitor who betrayed Bond in North Korea, forcing 007 to escape from Graves' facility. Bond then returns in his Aston Martin Vanquish to rescue Jinx, who has been captured once again. Zao pursues him in his own vehicle, both cars driving inside the rapidly melting ice palace. Bond kills Zao by shooting an ice chandelier onto him, and then revives Jinx after she has drowned.
Bond and Jinx pursue Graves and Frost to the Korean peninsula and stow away on Graves' cargo plane. Graves reveals his true identity to his father, and the true purpose of the Icarus satellite: to cut a path through the Korean Demilitarized Zone with concentrated sunlight, allowing North Korean troops to invade South Korea and reunite the peninsula by force. Horrified of the fact that it would result a nuclear war against the Americans, General Moon tries to stop the plan, but he is murdered by his own son.
Bond attempts to shoot Graves but he is prevented by one of the soldiers on board. In their struggle, a gunshot pierces the fuselage, causing the plane to descend rapidly. Bond engages Graves in a fist fight, and Jinx attempts to regain control of the plane. Frost attacks Jinx, forcing her to defend herself in a sword duel. After the plane passes through the Icarus beam and is further damaged, Jinx kills Frost. Graves attempts to escape by parachute, but Bond opens the parachute, causing Graves to be pulled out of the plane and into one of its engines, killing him and disabling the Icarus beam. Bond and Jinx then escape from the disintegrating plane in a helicopter from the cargo hold, carrying away Graves' stash of diamonds in the process.

Question: For what agency is Miranda Front an undercover agent?
Answer: MI6