At risk of sounding ignorant, I'll answer a one-liner:

Turn off the PC and boot Live Linux CD.

DETAIL:

If it's a Windows OS, turn the system off and boot a Linux Live CD. Backup your data and then clone the backup. Keep one safe and try running the other one under a clean OS.

If it's Linux then the ransomeware is designed to work under Linux, so same backup process, but then just run it under a different OS (i.e. *BSD, Windows, Android -built on Linux but vastly different in my experience-).

Of course, as the ransomeware developer said, you might as well let it finish. If you stop mid-process, you'll most likely never recover what has been encrypted already. You'll not have an ID to contact the developers with, and they probably might have not yet received your private key. Optionally, you can combine both. Use what I said earlier then simply boot the infected system back up and let it finish.

Declaimer: I'm a human potato; i.e. NOT a developer of anything

NOTE: As the 'best answer' seem to be more oriented to Advanced users (even to the level of incident response teams), this will be readily doable for any user with knowledge about Linux and Live CDs.

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At risk of sounding ignorant, I'll answer a one-liner:

Turn off the PC and boot Live Linux CD.

DETAIL:

If it's a Windows OS, turn the system off and boot a Linux Live CD. Backup your data and then clone the backup. Keep one safe and try running the other one under a clean OS.

If it's Linux then the ransomeware is designed to work under Linux, so same backup process, but then just run it under a different OS (i.e. *BSD, Windows, Android -built on Linux but vastly different in my experience-).

Of course, as the ransomeware developer said, you might as well let it finish. If you stop mid-process, you'll most likely never recover what has been encrypted already. You'll not have an ID to contact the developers with, and they probably might have not yet received your encryption key. Optionally, you can combine both. Use what I said earlier then simply boot the infected system back up and let it finish.

Declaimer: I'm a human potato; i.e. NOT a developer of anything

At risk of sounding ignorant, I'll answer a one-liner:

Turn off the PC and boot Live Linux CD.

If it's a Windows OS, turn the system of and boot a Linux Live CD. Backup your data and then clone the backup. Keep one safe and try running the other one under a clean OS.

If it's Linux then the ransomeware is designed to work under Linux, so same backup process, but then just run it under a different OS (i.e. *BSD, Windows, Android -built on Linux but vastly different in my experience-).

At risk of sounding ignorant, I'll answer a one-liner:

Turn off the PC and boot Live Linux CD.

DETAIL:

If it's a Windows OS, turn the system off and boot a Linux Live CD. Backup your data and then clone the backup. Keep one safe and try running the other one under a clean OS.

If it's Linux then the ransomeware is designed to work under Linux, so same backup process, but then just run it under a different OS (i.e. *BSD, Windows, Android -built on Linux but vastly different in my experience-).

Of course, as the ransomeware developer said, you might as well let it finish. If you stop mid-process, you'll most likely never recover what has been encrypted already. You'll not have an ID to contact the developers with, and they probably might have not yet received your private key. Optionally, you can combine both. Use what I said earlier then simply boot the infected system back up and let it finish.

Declaimer: I'm a human potato; i.e. NOT a developer of anything