WannaCry hackers withdraw over £100k after NHS ransomware attack

Businesses in 150 countries worldwide were affected by the ransomware attack, which led to demands of bitcoin payments to be made by the victims to the digital wallets of those behind it.

According to tracking firm Elliptic, three bitcoin wallets have withdrawn the money over the last 10 days.

Cyber security authorities advised businesses and organisations not to hand over the ransoms, which were for between $300 and $600.

NHS services throughout England were thrown into disarray in May when IT systems were disrupted by the large-scale cyber-attack.

Hospitals in London, Nottingham and Cumbria, among others, were simultaneously affected by the coordinated failure, amid several reports of pop-up messages on computers demanding ransom money.

Cyber-security has become a significant issue in recent months and years as both states and private entities become more aware of tactics aimed at disrupting networks across the globe.

"We're following the movement of funds being sent out of the WannaCry wallets," Elliptic co-founder Tom Robinson told CNBC.

"We believe some of these funds are being converted into Monero, a privacy-focused cryptocurrency. We continue to work with law enforcement to support their efforts in tracing ownership of these funds."