The user database probably was compromised as well, Bitcoinica's administrators said in an announcement posted on the site's home page. The information stored in the database included usernames, email addresses and account histories.

Account passwords were encrypted in a way that makes it extremely unlikely for them to be cracked, the Bitcoinica team said. However, to be on the safe side, the team advised users to change their passwords on other websites where they might have used them.

The compromised user information can be used to launch phishing attacks, as has happened in the past after many data breaches that exposed user email addresses.

Users should be suspicious of any messages received on their email addresses registered with Bitcoinica, the site's administrators said. "It is always a best practice to never click an email link to login to any online service."

is a cash-like digital currency that can be exchanged directly by users without the need for a central payment service. It uses the peer-to-peer model for synchronizing transaction records between users.