diff --git a/debian/resources/iptables.sh b/debian/resources/iptables.sh
index 1a14e8d..7e54280 100755
--- a/debian/resources/iptables.sh
+++ b/debian/resources/iptables.sh
@@ -26,6 +26,8 @@ iptables -A INPUT -j DROP -p udp --dport 5060:5091 -m string --string "exec." --
 iptables -A INPUT -j DROP -p tcp --dport 5060:5091 -m string --string "exec." --algo bm
 iptables -A INPUT -j DROP -p udp --dport 5060:5091 -m string --string "system" --algo bm
 iptables -A INPUT -j DROP -p tcp --dport 5060:5091 -m string --string "system" --algo bm
+iptables -A INPUT -j DROP -p sip --dport 5060:5091 -m string --string "multipart/mixed;boundary" --algo bm
+iptables -A INPUT -j DROP -p tcp --dport 5060:5091 -m string --string "multipart/mixed;boundary" --algo bm
 iptables -A INPUT -p tcp --dport 22 -j ACCEPT
 iptables -A INPUT -p tcp --dport 80 -j ACCEPT
 iptables -A INPUT -p tcp --dport 443 -j ACCEPT