First, the thief took all the BTC in my wallet. This was the transaction:
https://blockchain.info/tx/d6c75c6914c598d19fd6c0f73da0b009786e6585c57c6023ffbebdd6d7d0fecfI used the Bitcoin-QT wallet, but I used it without any password protection. Could that be the entering gate of the thief? The thing is that the machine is a newly installed windows and I did not download anything special to it.
As a consequence, I opened an online wallet on blockchain.info with mobile 2FA and including all the security options they provide. I imported the old private key from Bitcoin-QT, where my miner sent some minor BTC:
https://blockchain.info/tx/fee2c98ead5078127b3cbb8812332f1fa110f7326d65f0f577fa0e6ee38fe861Can this cause any risk to the new private key of the new BTC address? I will wait another week and the I delete this address from this wallet since my miner has still some immature BTC.
Thx for your advise and best regards