Multiple cyberattacks on major bitcoin exchanges this week highlight the many challenges for the young digital currency world.

A surge in investor interest also overwhelmed major bitcoin websites, while record-breaking levels of fundraising for new digital currencies add to worries that the largely unregulated cryptocurrency industry will be unable to manage the hype.

"Investors with assets on centralized cryptocurrency exchanges should be careful. The track records of these organizations are not good, and as the assets on the exchanges grow, so does the bounty for attacking or hacking them," said Benjamin Roberts, co-founder and CEO of Citizen Hex, a digital currency trading start-up backed by three Canadian venture funds.

Cyberattacks

Bitfinex, the largest U.S. dollar-based bitcoin exchange, said on its status website Wednesday morning that its platform was under distributed denial-of-service attacks, or DDoS, that attempts to paralyze a system with a flood of information.

The attack followed a similar one reported Tuesday morning. That problem was resolved within an hour, and the exchange said Wednesday that despite the "ongoing attack," "Most users will be able to use the platform normally though."

The news followed smaller BTC-e exchange's tweet Monday of a similar attack on its systems that afternoon, when its website also temporarily went down. By Wednesday morning, BTC-e had deleted the tweet and its website showed trades going through.

BTC-e and Bitfinex did not respond to CNBC requests for comment.