You could try adding the name of the encoder to the Flash Version String field.
If you are not sure what to put here, you can find by looking for a line like this in the logs:
You can edit this field at:
INFO server comment 2011-01-14 22:16:23 - - - - - 2.894 - - - - - - - - Flashver: Wirecast/FM 1.0 (compatible; FMSc/1.0)
And here is the guide for further reference:
Engine Manager > App name > Incoming Security > Flash Version String
How to configure security using Wowza Streaming Engine Manager