This follows reports the so-called Islamic State — which claimed responsibility for the attacks on March in Brussels and November in Paris — was receiving funding via the so-called Dark Web. This is the encrypted, hard-to-reach part of the internet where bitcoin or other digital-only currencies are the preferred payment methods.
"There is a shadow banking system that now exists around the world that is capable of moving unlimited amounts of money… They (terrorists or criminals) know the banking system is well-monitored," Scott Dueweke, the founder of Zebryx, a digital identity consultancy, told CNBC via phone.
In October, a report from the U.K. Treasury and Home Office concluded digital-only currencies were already the preferred method of online payment for illicit goods like firearms and drugs. The report added that the money-laundering risk associated with digital-only currencies was low, but could rise if their use became more prevalent.
A few months later, in January, Dutch authorities arrested 10 people accused of running a bitcoin-laundering ring.