A US Homeland Security official has said Bitcoin is “a lot more legitimate” as dark web users move away from the virtual currency.

Speaking in an interview with CNBC, the unnamed official said criminals were shying away from Bitcoin as law enforcement was “getting a lot better” at tracking them.

"I think [Bitcoin]'s a lot more legitimate than people give it credit for," the official added.

The issue of Bitcoin’s anonymity has long been a sticking point for illegitimate actors operating via the dark web, with more stealthy cryptocurrencies such as Monero seeing increasing numbers of Bitcoin refugees from the internet underworld.

Teaming Bitcoin with “legitimacy,” however, marks a turning point in official rhetoric from US state organs, which have overwhelmingly sided with those warning about its highly speculative nature and potential to lose investors money.

"What the criminals are starting to see, and some of the trends we're picking up as well, is that Bitcoin also works equally just as much against you as it does for you,” the CNBC source added.

In July, the largest Bitcoin tumbler service Mixing Bitcoins announced it was ceasing operations permanently.

Tumblers attempt to increase the anonymity of Bitcoin transactions by making it impossible to ascertain which specific address a transaction originated from.

“I hope our decision will help to make Bitcoin ecosystem more clean and transparent,” the service wrote in a note to competitors.

“I hope our competitors will hear our message and will close their services too. Very soon this kind of activity will be considered as illegal in most countries.”