Quote from: Specular on January 05, 2015, 06:26:16 PM

From Reddit - https://www.reddit.com/r/BitcoinMarkets/comments/2repff/bitstamp_exchange_issues_megathread/cnf6gdp

user baron1703 wrote:

Observations:

Known Bitstamp cold storage: https://blockchain.info/address/1JoktQJhCzuCQkt3GnQ8Xddcq4mUgNyXEa

Suspicious address: https://blockchain.info/address/1L2JsXHPMYuAa9ugvHGLwkdstCPUDemNCf

Transactions started to appear in the suspicious address after 1am european time on 04.01.15. The first transactions had fees of 0.55 and 1 btc, respectively. These continue thought the day with fees of around 0.1btc. First complaints of deposit issues started during the day. Stamp sent out an email the NEXT day, shortly thereafter suspending its site.

As can be seen here (http://www.walletexplorer.com/wallet/6e20c5b8ebb819c7?from_address=1L2JsXHPMYuAa9ugvHGLwkdstCPUDemNCf), the transactions coming into the 1L2JsX address are from bitstamp addresses (note that this page is not real time, so not all new transactions are displayed).

The cold storage address mentioned above was not touched since mid december. The first new transactions in this address appear at around 10pm european time on 04.01.15. This appears to be a sweep of hot wallet addresses and brings in about 10k btc. Notice the specific structure this sweep transaction has (example: https://blockchain.info/tx/c84a1b8e7aaeae81cf3a1db7e37fdd6befbedafb4213338f412c6981b9469553) - a round amount is swept to the cold storage, an arbitrary amount is put in another address where it is combined with other inputs and swept again. This pattern is not observed in the 1L2JsX address. Furthermore, fees in the cold storage address vary from 0.0001 to 0.001, depending on size - again, unlike the 1L2JsX address.

IF the 1L2JsX address indeed belongs to a hacker, bitstamp COULD be missing 18,865btc, with the remaining 134,872btc in its cold storage wallet. It appears that only these two addresses have been used for sweeping. This would imply a loss of 12% of all held bitcoins.

One of the bitstamp founders (https://twitter.com/nejc_kodric) tweeted: "To restate: the bulk of our bitcoin are in cold storage, and remain completely safe." Interpret that as you will.

http://oi59.tinypic.com/2lmmc6v.jpg