Windows 10 April 2018 Update removes Npcap Loopback Adapter

[dmiller-nmap]

No clues yet on why or how, but it's gone. Npcap 0.99-r5

Running NPFInstall.exe -ul then NPFInstall.exe -il restores the adapter, but Nmap isn't able to use it, giving the dnet: Failed to open device lo0 error message.

Reinstalling Npcap creates a new, working Npcap Loopback Adapter.

[dmiller-nmap]

Just remembered: I did not restart the npcap service after running the NPFInstall.exe commands, which was probably required in order for Npcap to know about the change. Full reinstall is probably not required, just the loopback uninstall and install, then restart the driver service.

I will be checking the upgrade logs for messages related to the Npcap Loopback Adapter to see why it was removed.

[dmiller-nmap]

Update: this affects all Microsoft KM-TEST Loopback Adapter devices installed on the system, and happens even if Npcap is not installed. It is not exclusive to Npcap.

[dmiller-nmap]

This still happens, but now it only affects "Legacy loopback support" installations, since loopback capture and injection is now handled without the Npcap Loopback Adapter.

[dmiller-nmap]

Legacy loopback support with the Npcap Loopback Adapter is now strongly deprecated. We do not intend to address the problem of Windows feature updates removing the adapter. Recommended fix is to reinstall without this feature.