Bitstamp is in the process of restoring full services to all accounts following an issue that prompted the bitcoin exchange to disable withdrawals to some users.
The move was a security precaution and the affected accounts have been notified of the problem.
Nejc Kodrič, Bitstamp's CEO, told CoinDesk that some accounts have already regained withdrawal functionality.
The decision to halt the withdrawals was made after Bitstamp detected an increased number of phishing attempts over the last few days.
Bitstamp says some clients had reported receiving suspicious emails. The correspondences were examined and were found to contain malware, so Bitstamp then took the 'better-safe-than-sorry' approach and temporarily disabled the accounts.
At the time of writing, no Bitstamp user has reported any missing funds. It is possible that the attack was completely unsuccessful, although it is still too early to say with certainty.
Bitstamp believes the attack was targeted at bitcoin users only, and its sole intent was to steal bitcoins.
In an email sent to affected clients, the Bitstamp team stressed that the tech team's response to the phishing attack was a necessary precaution given the risks of the situation, and gave advice on how to deal with any malware.
"As a precaution we have also applied this security measure to your account," the exchange wrote. "If you have received any emails with suspicious content and have opened links or attachments, we highly recommend that you immediately contact a computer expert."
Even if you think your computer is clean, it is probably best to play it safe, Bitstamp says:
"If you consider that your system was not affected we kindly ask you to contact firstname.lastname@example.org to re-enable the withdrawal function on your account."
The company added that the decision to disable withdrawals is an inconvenience, but it should be viewed as part of the exchange's important security measures, which were put in place to safeguard users' accounts – and their funds.
The Mt. Gox debacle is still in the news, and other exchanges – including Bitstamp – have also faced related and unrelated problems in recent days.
Last week, Bitstamp was targeted by a massive DDoS attack, along with a few other exchanges. As with the current issue, it was forced to suspend processing bitcoin withdrawals, but it quickly recovered and resumed regular service.
On a more positive note, most exchanges appear to be very resilient to the frequent DDoS and targeted phishing attacks. It comes with the territory, it seems, and it is reassuring to see that most sites spring back to full service in a matter of hours.