Shorewall users - Sep 2014 - Interpret this code Iptables in Shorewall (--string 'var')

This code is in Iptables rules ... Close port 443 to sites facebook in port
443 (https), How I can interpretet in shorewall ?

iptables -I FORWARD -p tcp --dport 443 -m string --string 'facebook'
--algo
bm -j DROP


Thanks !!


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