Linux Packet Filtering and iptables - LOG target options
https://www.linuxtopia.org/Linux_Firewall_iptables/x4238.htmlOption--log-level: Example: iptables -A FORWARD -p tcp -j LOG --log-level debug: Explanation: This is the option to tell iptables and syslog which log level to use. For a complete list of log levels read the syslog.conf manual. Normally there are the following log levels, or priorities as they are normally referred to: debug, info, notice, warning, warn, err, error, crit, alert, emerg and panic.