IMDB / United Artists Some of the world's biggest banks are hiring former spies to try to prevent the rise of any more so-called rogue traders and generally ensure that banks are put on the hook for fewer fines.

According to a report from Bloomberg, banks including HSBC, Deutsche Bank, and JPMorgan have hired ex-spies from the likes of the UK and US militaries, the CIA, and GCHQ to watch the activities of bank employees and try to prevent misconduct.

Bloomberg cites information provided by recruitment firms, executives, and compliance officers to show that banks are using former spooks to keep tabs on activity as varied as cigarette breaks and texting with a significant other, all to spot the early signs of rule breaking.

In recent years, bank employees including Jerome Kerviel, Kweku Adoboli, and Tom Hayes have been jailed for their roles in big banking scandals.

In 2008, Kerviel lost €4.9 billion (£3.7 billion) at Societe Generale, and Adoboli's trades left UBS on the hook for $2 billion (£1.4 billion) in 2011. Hayes was involved in the fixing of the Libor rate, though his sentence was reduced after an appeal.

Not only are these sort of scandals hugely embarrassing for banks, but they can also be incredibly costly. The Libor scandal, for instance, cost six banks a combined total of about $6 billion (£4.15 billion), with Barclays alone footing a bill for $2.2 billion (£1.5 billion).

Increased scrutiny on the banking sector, thanks in large part to stricter stances from regulators like the US Securities and Exchange Commission and the UK Financial Conduct Authority, has led many financial institutions to take big steps to try to keep such scandals from occurring again and costing them billions.

Bloomberg cites Chris Mathers, a former Canadian police officer, now a consultant, who said, "The biggest threat to banks today, the absolute biggest threat, is the regulator."

In an era in which profits are getting more and more squeezed, the ability of banks' balance sheets to absorb big fines is getting smaller. UBS announced plans in 2015 to bring in about 350 new compliance employees after being hit by a series of big fines, including penalties related to Adoboli's misconduct.