To keep a long story short, I got hacked on my PC by downloading and executing a wrong file. Programs as InterVPN, Cryptobot and HVNC (told by the hacker via google chat) were installed. My accounts (Outlook and Gmail) were taken over.
They used my passwords (stored in Google) to try to log in to a lot of cryptocurrency-accounts. And my specific question is regarding their succesfull login into Blockchain. The 2FA via sms was activated, but still they managed to get into my account.
When googling, I find things like Sim-swapping, but that seems highly unlikely, because I received the text message myself. Spyware on my phone is another way, but it appears it must always be installed on the phone itself, which is not possible (phone always with me, everything started after downloading that file, and hackers probably 1000 miles away). Also a scan afterwards didn't show anything. Also all this happened a few minutes after downloading the file, so everything went quite fast.
10 minutes after the text messages, they were able to transfer funds of my account to another. So maybe they needed some time after they saw that 2FA was necessary.
All this was/is quite terrifying (lost money, been blackmailed, ...), but most things that happened on PC I can understand, but I can't understand how they were able to log in to Blockchain without knowing the text message, or ... did they know the sms message, but then how? Keep in mind that everything went quite fast, and that I'm sure that they didn't focus me before downloading that file. My phone number was available in my Google account.
I now took measures to prevent this from happening (re-installed PC completely), but as long as some questions stay in my head, I can't remain calm about this. And of course I'm a bit psycho on how safe my phone really is.
Best regards and thanks for the answers and advice!