The sudden crisis at Bitstamp appears to have escalated from one of warning users not to deposit bitcoins and into a scenario whereby history may be repeating itself. The Bitstamp website has now been shuttered in order for security staff to assess the "security and soundness" of the exchange. The website now reads:

Bitstamp Service Temporarily Suspended

We have reason to believe that one of Bitstamp’s operational wallets was compromised on January 4th, 2015.

As a security precaution against compromises Bitstamp only maintains a small fraction of customer bitcoins in online systems. Bitstamp maintains more than enough offline reserves to cover the compromised bitcoins.

IN THE MEANTIME, PLEASE DO NOT MAKE DEPOSITS TO PREVIOUSLY ISSUED BITCOIN DEPOSIT ADDRESSES. THEY CANNOT BE HONORED!

Customer deposits made prior to January 5th, 2015 9:00 UTC are fully covered by Bitstamp’s reserves. Deposits made to newly issued addresses provided after January 5th, 2015 9:00 UTC can be honored.

Bitstamp takes our security and soundness very seriously. In an excess of caution, we are suspending service as we continue to investigate. We will return to service and amend our security measures as appropriate.

Bitstamp Team

Despite Bitstamp's promise that customer deposits¹ are fully covered, no specific information as to the total amount of bitcoins which have likely been either lost or stolen is known at this time. This also calls into question how Bitstamp intend to guarantee deposits in the future if they can arbitrarily decide not to honour deposits.

According to data taken from bitcoinaverage.com, Bitstamp had processed 40,240.23 BTC in trades over the past day prior to the shut down. This number likely represents a large number of former owners who's coins are now inaccessible, will remain so for an unknown period of time and are at the mercy of Bitstamp who will now decide if and when they will allow customers to regain control of said coins.

1. Made prior to January 5th, 2015 9:00 UTC. ↩