Help—I currently have Avast Internet Security and it seems to be blocking access to a Network Attached Storage (NAS) Drive that I own. It is a Western Digital “My Book Live” network connected drive. I can see it using my browser and Windows 10 file explorer, but the AVAST program seems to be somehow blocking my WD Shareware backup program from seeing the drive. I have tried excluding the drive’s URL but no help. Only when I disable the AVAST shields is that the WD Shareware program can see the drive.
Hello,
I have the same issue of Avast preventing access to network shares on NAS. This happened once before and the issue was caused by a faulty program update. The solution was to download the latest software from Avast and manually install. This fixed the problem cause by the automatic update in the program.
The first issue was with Avast Internet Security 11.1.2245 at the end of December 2015. I know have 11.2.2262 with the problem, but the manual install hasn’t worked.
What version of AIS are you running?
And have you tried a manual download/install?
A couple notes for Mike or anyone else who has this problem.
#1 stopping the avast services does not affect the problem. This drove me crazy when it first happened. I first thought since disabling avast services didn’t fix the issue that it wasn’t an avast issue. But uninstalling avast fixed it.
#2 other than not being able to access network share folders, the only other symptom I could see was in Device Manager, aswNetSec has the wanring “this device is not present, is not working properly, or does not have all its drivers installed.”
#3 the first time this happened I was able to install the download from avast over the installed version. This time I had to do a complete uninstall, reboot, and then reinstall.
HTH 
You can try excluding the backup program from the scan on executing.
You can also try to add the path to Network Drive in the Exclusions list.