Microsoft Windows machine can be perfectly safe. Let's say it's dedicated to run your full node and nothing else.
What hackers can do in such situation?
Well winblows is a black box and therefore you can NEVER assume it can be perfectly safe.
The list of compromised services is so lengthy I don't even think there is a comprehensive list available.
Here is a list (not complete) of services you should have disabled that allow remote ports to be opened on your system.
If you aren't running your home LAN behind a managed firewall (I use a Redhat-based product), then you aren't doing local security well.
Default rules should be block everything incoming at the Firewall, and only port forward as necessary to machines. Disable ICMP pinging at the firewall as well if you want to be extra careful.
I've moved my full node over to a Windows 10 install, after getting sick and tired of the thermal controller on the IBM server I was using, needing an update, and didn't have updates available for Ubuntu (Only Redhat and Windows. Thanks IBM. Fuckers.) Used a free tool to copy the ext4 bitcoin directory data over to an NTFS volume, and I was off to the races again.
In theory, port forwarding should be "secure enough", assuming
doesn't become exploitable at some point...