drop packets for specific port with iptables
 

I want to drop the traffic generating from my client's webcam using iptables mangle rule. How can I do that?

iptables -t mangle -A OUTPUT -p xxx --sport xxx -j DROP

then use

iptables -t mangle -vnL to verify that either packets hitting the rules or not.

but you can also block this on filter tables's output chain.

also please note that mangle table's input and output chains are not available in old iptables versions, which were included in distributions like redhat 7.2/7.3 .