Banks are now hiring staff to listen in on traders' conversations, after banter was found to flummox sophisticated surveillance technology, according to a new report on market abuse.
The report from professional services firm PwC discovered that banks plan to spend £156m on surveillance technology over the next 18 months to make sure that trading teams are not abusing the market, but still rely on the human touch to accurately pinpoint the true meaning behind some calls and messages.
Teams listening to phone calls are also growing, as automated phonetic and transcription voice technologies are increasingly being looked at but are not yet seen as a proven substitute for manual review, according to the report.
Graham Ure, forensics partner at PwC, added: "140,000 people work in banking in the City of London alone. That equates to tens of billions of emails, messages and phone calls every year.
"In a fast moving environment, those communications often use highly colloquial or coded language. And to be truly effective, surveillance needs to be able to spot new or emerging forms of abuse – likely to involve only a few traders and a handful of transactions – in this ocean of data."
Banks are no doubt feeling pressure to step up their surveillance after a slew of high-profile cases. Interbank rate and foreign exchange market rigging has already seen banks shell out nearly $20bn (£13.8bn) in fines worldwide.
Ure added: "Banks are taking surveillance much more seriously and backing that commitment with investment. They are building bigger teams and increasing their surveillance spending."