'Vietnamese hackers' are suspected of bombarding a retired civil servant with threatening phone calls and emails.
David Goodman, 58, of Tudor Road in Chingford, was surprised to receive an email confirming the £1,000 purchase of four electric drills from Screwfix.
Despite holding an account with the retailer, Mr Goodman did not place the order.
He immediately phoned the company and found the goods were due to be delivered to a council building in Coney Burrows, Chingford.
Mr Goodman then received a phone call from the fraud department at Sainsbury’s Bank regarding a £1, 2823 purchase and two other attempted purchases of £4,200, both of which he had no knowledge of.
Then within hours he started receiving menacing phone calls from a man with a British accent who claimed to represent a group of hackers based in Vietnam.
He told Mr Goodman to check his email and follow a list of instructions.
"He told me if I don't follow their instructions and comply by today, they will drain my bank accounts, destroy my identity, damage my business and steal my house from me," Mr Goodman said.
Mr Goodman said he “froze” with fear and then received four more phone calls in 10 minutes, which led him to disconnect his phone.
He added: "It was a terrible shock. I froze and listened to what he said but I didn't know what to say. I've taken this very seriously and think it is a genuine threat.”
The retired Ministry of Defence employee subsequently found all his emails had been deleted - but one.
The email ordered him to pay $1,000 US dollars to someone in Vietnam through Western Union by yesterday.
Mr Goodman said he regained his composure before driving to Chingford police station to report the threats.
But the phone calls continued yesterday, prompting Mr Goodman to freeze his bank accounts, cancel his cards and make arrangements to change his phone number.
Action Fraud UK, an agency which handles reports of online fraud, is investigating the case.
A spokeswoman for Screwfix said: "We take the security of all our customer data very seriously and we can categorically say there has been no breach of any of our data systems.
"We want to reassure all our customers that they are fully protected when shopping with Screwfix."