Can anyone tell me if there is a way to identify the culprit of an "Invalid Username or Password" error in ArcGIS Server logs? For source, it just says 'Admin' for source, and nothing for User. Is there a .txt log stored somewhere that would tell me which username is causing the bad login?
It looks like you should be able to now that I have read up a bit on the documentation. It looks like you can check User Name if you set it up in the Logging Properties. Check the documentation HERE to find more details.
From what I am gathering, you just need to add a property. You also could look into setting your Logging Level to Debug if you can't get the information through the properties.
This is for 10.1 so hopefully your version is around there.