Bitcoin tops $17,000; NiceHash hack raises concerns ahead of US trade

At the start of the year, one bitcoin was worth less than $ 1,000

Bitcoin surged past $17,000 on Thursday as the frenzy surrounding the virtual currency escalated just days before it starts trading on major US exchanges.

Bitcoin has gained more than $5,000 in just the past two days.

At the same time, there are fresh concerns about the security of bitcoin and other virtual currencies after NiceHash, a company that mines bitcoins on behalf of customers, said it is investigating a breach that may have resulted in the theft of about $70 million worth of bitcoin.

Research company Coindesk said that a wallet address referred to by NiceHash users indicates that about