Actually this is only possible for Event Log events - because Splunk has to parse them, even on a Universal Forwarder. Since Splunk has to translate the event log binary to text before it is forwarded, it seems logical to add the capability to filter the events locally.
However, no other data inputs are parsed during the inputs phase. Therefore, the events cannot be filtered using a Universal Forwarder.
If you must filter the events locally, you can use a Heavy Forwarder, which processes both the input phase and the parsing phase before forwarding. Be aware that this will increase the processing load on the local machine, which is usually a bad idea for a forwarder that lives on a production server.
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