High-level hacking, industrial espionage and infrastructure-debilitating online attacks are imminent threats to U.K. banks, a top British cyber spy said, urging bankers to join a work placement scheme at an offshoot of the secretive Government Communications Headquarters to learn how to deal with the risks.

"It is a realistic possibility that state-sponsored actors will seek to compromise U.K. financial institutions," said the GCHQ agent, introducing himself as Lewis, and chairman of the committee that oversees information exchange between the industry and the state security service.

A spokeswoman for GCHQ, the U.K.'s communications and online monitoring secret intelligence agency, confirmed that 'Lewis' was one of its agents and told S&P Global Market Intelligence that employees of the British security services are not allowed to reveal their real names when speaking publicly.

The cyber world is an increasingly dangerous place for bankers, the spy told a London banking conference organized by research company RBR on Oct. 9, noting that organized crime groups often work in conjunction with sanctioned states such as North Korea and Russia to infiltrate banks to extract money and information, or simply to disrupt operations.

Bank of America Corp. and U.S. Bancorp were, for example, among several U.S. financial institutions said to be onetime targets of North Korean hackers, according to a March 2017 report by The New York Times.

Such activities could further the "strategic objectives" of the U.K.'s adversaries, Lewis said. He also said that although the U.K. signed a cyber amnesty agreement with China in 2015, the Asian country poses a significant threat.

To counter these threats, GCHQ has opened a temporary placement program that allows bankers to join its own teams to learn from spies, Lewis said. So far, GCHQ has admitted 40 "industry secondees" and 50 more were in the process of joining, with firms already "seeing the benefits."

The National Cyber Security Centre, which was established in October 2016 with the aim of being the more visible arm of GCHQ, recently accused Russia of committing a series of cyberattacks around the world.

The NCSC said Russia's military intelligence agency, the GRU, had attempted to infiltrate the computers of the U.K. Foreign Office in April and March 2018, around the same time that former GRU officer Sergei Skripal was poisoned in Salisbury, which was also attributed to the GRU. 'Lewis' warned that the GRU also posed a threat to banks.