Despite the widespread notion that the blockchain technology behind bitcoin and other cryptocurrencies is safer and more trustworthy than that underlying other kinds of digital financial transactions, startups in the industry have struggled to secure their sites and software against hackers.
NiceHash is a digital currency marketplace that matches people looking to sell processing time on their computers in exchange for the digital currency bitcoin.
NiceHash, one of the most popular crypto-mining marketplaces, has apparently suffered a breach that resulted in the theft of the entire contents of the NiceHash Bitcoin wallet. Bitcoin can only be used as a medium of exchange and in practice has been far more important for the dark economy than it has for most legitimate uses.
Another NiceHash user Philip Richardson tweeted: "If I don't get my btc back I will never use your service again". That could involve significant sums: it paid out millions of dollars in bitcoin every week, according to its official Facebook page. "We are working to verify the precise number of BTC taken", it added.
While NiceHash has yet to place an amount on how much is stolen, a Bitcoin wallet address highlighted by NiceHash users that appeared Wednesday and has received a large deposit out of nowhere contains 4,736.42 BTC, valued at about $62 million at current prices.
It wasn't immediately clear whether funds had been taken from NiceHash users' accounts as well.
NiceHash users typically mine altcoins in exchange for their value in Bitcoin.
Earlier, Slovenia-based NiceHash said in a statement posted on its website that it had halted operations for 24 hours as it investigated the breach.
The company did not respond to requests for comment.
The cyber heist is yet another reminder about the vulnerability of some digital currency platforms.
The company confirmed the hack today, but did not release totals.
Cybersecurity firm FireEye warned recently that North Korean hackers are stepping up their attempts to steal bitcoin in order to support Kim Jong Un's authoritarian regime.