Police in Calgary, Winnipeg, Toronto, Hamilton, Halton and other Canadian centres after hunting for four men seen above who stole almost $200,000 by employing a trick known as a double spending attack.
The first suspect on their radar is believed to be the brain behind the attacks in Hamilton, Montreal, Ottawa, and Toronto; the second suspect is reportedly responsible for the 51 fraudulent transactions in Calgary; and suspects #3 and #4 allegedly responsible for the attacks in Winnipeg and Sherwood Park respectively.
Police say the suspects committed "double-spend attacks" in which they withdrew money from a bitcoin kiosk and then remotely cancelled the transactions before the withdrawal was processed.
Four suspects have been caught on surveillance footage, and are all described as adult men who likely have in-depth knowledge in cryptocurrency, bitcoin, and blockchain technology.
This man is suspected of making fraudulent transactions in Toronto, Montreal, Ottawa and Hamilton.
Calgary is home to a total number of 45 Bitcoin ATMs, but only 21 of them support Bitcoin sales. They seemingly managed to steal the funds by taking advantage of the Bitcoin ATMs accepting 0-confirmation transactions. That creates two transactions in succession, one paying a specific amount to a specific address, and a second one double-spending that transaction. That is why services ask for multiple confirmations for every transaction.
While bitcoin double-spending is not much heard of, it is not completely impossible.
The Calgary Police Service's cybercrime team has been leading a national investigation into the fraudsters since October with assistance from agencies across the country, including the Toronto Police Service, Hamilton Police Service, Winnipeg Police Service and Halton Regional Police Service.