[desumeku]

In order for transactions to be signed with the private key, the device holding them has to be connected to the internet, or at least be able to interface with another device that is. It is highly likely that anything involving their BTC reserves requires someone to be physically present at some sort of facility and it is 100% not available for hackers to just siphon whenever they wish with a virus. If possible, it would at least require physical infiltration.

[wyck]

That's what cold storage is. And more than likely cold storage they requires multiple signatures, to prevent any single entity from being compromised.