How to block Skype - working script

iptables -I FORWARD -s 111.221.74.0/24 -j DROP
iptables -I FORWARD -s 111.221.77.0/24 -j DROP
iptables -I FORWARD -s 157.55.130.0/24 -j DROP
iptables -I FORWARD -s 157.55.235.0/24 -j DROP
iptables -I FORWARD -s 157.55.56.0/24 -j DROP
iptables -I FORWARD -s 157.56.52.0/24 -j DROP
iptables -I FORWARD -s 194.165.188.0/24 -j DROP
iptables -I FORWARD -s 195.46.253.0/24 -j DROP
iptables -I FORWARD -s 213.199.179.0/24 -j DROP
iptables -I...