Detectives have arrested a 32-year-old man in connection with a suspected £1m of fraud following an electronic attack on HM Revenue & Customs computer systems.
Police and HMRC began a joint investigation in June after HMRC identified an electronic attack and alerted officers from the Police Central e-Crime Unit (PCeU).
The investigation is looking into a criminal network which is believed to be stealing money from HMRC by making fraudulent claims through the self-assessment tax repayments system.
Detective Chief Inspector Terry Wilson from the PCeU said, "This is a complex operation by the Met and HMRC and shows how such e-crime attacks and frauds are being identified and taken very seriously by both organisations.
"The issue of e-crime is a growing problem across all business sectors and on-line services but working with our partners in government and industry we are committed to ensuring that criminals do not find the internet a safe environment to operate in, and that those operating internet services have the full protection of law enforcement."
Police arrested the man at his home in Poplar, East London in the early hours of this morning, on suspicion of fraud and money laundering. He is currently in custody at Bethnal Green police station.