North Korea is seeking to profit from Bitcoin's surging value by hacking Bitcoin exchanges, security researchers have told Sky News.
Ashley Shen, an independent security researcher, said: "We assume one of the reasons why Bitcoin is being attacked is because the price keeps increasing and we think it's reasonable for hackers (to target).
"Digital currency might be easier to gain than physical currency. So I think it's reasonable."
Bitcoin's value has risen dramatically over the course of 2017, but especially during the past week, peaking at one Bitcoin being worth $16,000 (£11,940).
The currency's value is up 1,500% this year, driven by sheer speculation.
Ms Shen and her colleagues have tracked attacks by hacking groups Lazarus, Bluenoroff and Andariel – suspected to be North Korean operations – on financial institutions including banks in Europe and South Korea, an ATM company and Bitcoin exchange.
She told Sky News: "Before, when we tracked nation-state attackers, they usually perform cyberattacks which are aimed for confidential data and intelligence.
"However recently we've discovered that some of the APT (Advanced Persistent Threat) groups are trying to hack financial institutions like banks and Bitcoin exchanges to gain financial profit."
Ms Shen said the attacks had so far been unsuccessful.
"My own opinion is they will probably keep doing the Bitcoins because the price keeps increasing and it's a good investment… So I assume they will do more Bitcoin attacks and of course they will keep targeting banks because that's what they did before."
One of her co-researchers, who wishes to remain anonymous because they work for a South Korean bank, told Sky News: "Just a few years ago the attacks were initiated to paralyze the society, but for sometime now they've been hacking for money – so I kind of wonder if they are facing financial difficulties."
As Bitcoin has surged in value, particularly over the last week, it has become increasingly attractive to hackers.
On Thursday, Bitcoin mining marketplace NiceHash, based in Slovenia, suspended operations after hackers stole 4,700 Bitcoin – at the time worth roughly $64m.
The National Crime Agency told Sky News: "The vast majority of cryptocurrency use is not criminal. Bitcoin is one of more than 1,000 cryptocurrencies and many people use cryptocurrencies to bank or to transfer money or make investments.
"We do see cybercriminals using cryptocurrencies as one of a range of ways in which criminals try to launder money.
"But criminals are mistaken if they believe that cryptocurrencies are untraceable and provide total anonymity.
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"Many dark web and online marketplaces where illegal commodities are bought and sold rely on cryptocurrencies. The NCA conducts operations against criminal activity on the dark web and is alert to criminal threats which rely on its use.
"We're also seeing that traditional crime groups are starting to use the Bitcoin network to store and transfer value, and using ATMs and peer-to-peer exchanges to cash in or out of the network."