The syslog-ng 3.0 Administrator Guide

To skip the processing of a message without sending it to a destination, create a log statement with the appropriate filters, but do not include any destination in the statement, and use the final flag.

	Example 7.1. Skipping messages
	The following log statement drops all debug level messages without any further processing. filter demo_debugfilter { level(debug); }; log { source(s_all); filter(demo_debugfilter); flags(final); };