Today's arrests follow an investigation into an apparent online scam whereby £1 million was siphoned off the accounts of customers of two banks.
The alleged scam involved emails, that appeared to be from the banks, containing "malware" which corrupted the recipients' computers.
T/DCI Jason Tunn of the Metropolitan Police's Cyber Crime Unit said he suspects they are dealing with an "international and organised crime targeting a number of bank customers in London and across the UK".
"The victims have been hoodwinked by malware-carrying emails purporting to be from their banks, and subsequently had money taken from their accounts," he said.
More top news
Outbreaks of rain and strengthening winds will affect southernmost parts of England and Wales today.
An earlier debate on the issue was suspended as an 'expression of support' following the Westminster terror attack.
Five people were killed and dozens more were injured after a car and knife attack in the capital on Wednesday afternoon.