I still run XP because many of my development tools will not run an the newer bloatware. The XP machine does hide behind a Linux firewall. This has proven to be fairly robust.
I run XP occasionally as well, but purely because I run some high-end CAD/CAM programs that will only run on XP.
I simply make certain that I am disconnected from the net when I work with them.
Only slipped up once over the years, and when I noticed the computer was transmitting and downloading data in the background, I promptly disconnected, shut it down then restarted it with a Boot Disk and reloaded the OS.
No worries after that.