We had another situation yesterday that probably explains Tim's comments about some people replacing Win Defender with a different firewall to solve the Win 10 April edition issues.
One of our apps, running on a Win10 April edition workstation, would freeze 10 secs after startup. It was pulling the exe from the shared network drive which is how we install all our apps.
We tracked the freeze to a timer that opened a listening socket 10 secs after the app started.
This blocking listening socket was not responding and because the app is single threaded it hung the whole app making it freeze
We copied the exe to local C drive and ran it from there and the problem went away.
This happened because Windows Defender was blocking the socket/port when we ran the exe off the network drive. Win Defender did not block the socket if we ran the exe off the local c: drive.
This makes sense - Win Defender would apply stricter rules to network originated exe's
We examined Win Defender setup and found that while It allowed the exe to be loaded from the network drive, it was blocking the app's listening socket connection when the exe was loaded from the network drive
We tried to remove this rule from Win Defender / allow the listening socket but found it very difficult / impossible to change the Win Defender config or to disable the Win Defender service, which I suppose is exactly what MS want!, which is why some users would have just un-installed it.
NB On this particular Win10 workstation, IT staff had re-enabled SMB1 (because the old Linux server did not support SMB2). We re-tested running the app on a different Win10 April edition workstation using SMB2 with the exe pulled from the server drive - no issues at all
Conclusion:
As part of discouraging use of SM1, MS did the following in the Win 10 April edition
- disabled SMB1 protocol
- changed Win Defender to apply stricter rules to SMB1 traffic (vs SMB 2) traffic, for Win 10 workstations if SMB1 is re-enabled
SMB1 is ancient and is the protocol that is abused by many viruses to discover and spread to multiple networked machines easily and quickly. In our modern world we must simple not use it, it is not secure enough, unless you particularly want to be a ransomware victim…
Peter