Eight men have been arrested in connection with a £1.3m theft by gang who took control of a Barclays Bank computer.
The money was transferred from the branch in Swiss Cottage in north London in April, a Met Police spokesman said.
Searches are being carried out at addresses across London and the men were arrested on Thursday and Friday.
Following the report of the theft, police found a "keyboard video mouse" switch attached to one of the branch's computers. It was installed as one of the gang pretended to be an IT engineer the day before the theft on April 5. A Keyboard Video Mouse switch, which has a 3G router attached, allows a user to control multiple computers. This enabled the gang to remotely transfer funds to other back accounts. Barclays said it was able to recover a "significant amount" of the stolen money.
One central London premises which was been searched was described by detectives as the "control" centre for the fraudsters.
"Those responsible for this offence are significant players within a sophisticated and determined organised criminal network, who used considerable technical abilities and traditional criminal know-how to infiltrate and exploit secure banking systems," Det Insp Mark Raymond of the Met's Central e-Crime Unit said.