Use Integrity Monitor Policy.
Under file tab include c:\abc directory.
Under extension tab, exclude bak
If I configure the policy like you suggest, I am afraid the *.bak will be excluded from all paths, not only c:\abc and subfolders.
Let's say I also have another folder assigned to be monitored c:\123 and in that path I want *.bak included in monitoring.
How to solve this?
Use filters tab.
File begins with C:\abc
file ends with bak
Ok, for my initial task I found following solution. Not the nicest.
File begins with c:\abc
file does not include .bak
(because there is not such condition like "Does not end"