Although candidates are usually required to keep their applications secret, the former EastEnders actor said that has responded to an online advert for a Mobile Surveillance Officer with the secret service.
"I've got an enquiring mind, so I thought I'd give it a go," he told The Sun. "I love spy films and the whole James Bond thing.
"MI5 put out an advert looking for people and I thought, 'How hard can it be?' Most spies spend their lives pretending to be people who they're not. I do that for a living."
The MI5 job advertisement read: "Join us as a Mobile Surveillance Officer at MI5 and help keep people across the UK safe.
"A valued member of a diverse team, you'll follow subjects of national security investigations by foot and by car.
"Your observation skills, quick thinking and ability to fit into your environment means you'll be able to make a big contribution."
A friend of Gaffney's stated that he applied for the job after struggling to find acting work in recent years.
"There wasn't much acting work around so Dean had a look at what else was out there," the friend said.
"That's when he saw the MI5 advert and figured it was worth applying. He's not heard back yet - but fingers crossed."