Movies You Haven't Seen But Should: Cypher

Wiki:

Cypher is a Canadian sci-fi thriller released in 2002, directed by Vincenzo Natali and written by Brian King. It stars Jeremy Northam and Lucy Liu.

Morgan Sullivan, a recently unemployed accountant, is bored with his suburban life. Pressured by his wife to take a job with her father's company, he instead pursues a role in corporate espionage. Digicorp's Head of Security, Finster, inducts Morgan, and assigns him a new identity. As Jack Thursby, he is sent to conventions to secretly record presentations and transmit them to headquarters. Sullivan is soon haunted by recurring nightmares and pain in the back of his neck. When he meets a mysterious woman, Rita Foster, from a competing corporation, his life starts to get complicated.

[Cypher on the IMDB]