Bitcoin transactions cannot be undone. Once a transfer of bitcoins is sent out into the network, it cannot be revoked. So a hacker with access to the computer where your Bitcoin wallet is stored can send your entire bitcoin wealth to another wallet without anything being done about it afterwards.

If the computer with your Bitcoin wallet is owned by a third party that has insured this computer against theft – this applies, for example, to any reputable Bitcoin wallet hosting service – then of course it is possible that all or part of the lost amount will be replaced. Bitcoin wallet hosting service Instawallet recently shut down after a catastrophic hacker attack and paid compensation to all users who had lost 50 bitcoins or less.