diff -up ntp-4.2.6p5/ntpd/ntp_proto.c.sourceport ntp-4.2.6p5/ntpd/ntp_proto.c
--- ntp-4.2.6p5/ntpd/ntp_proto.c.sourceport 2015-02-06 16:43:27.857879763 +0100
+++ ntp-4.2.6p5/ntpd/ntp_proto.c 2015-02-06 16:43:56.446879712 +0100
@@ -334,7 +334,7 @@ receive(
* reveals a clogging attack.
*/
sys_received++;
- if (SRCPORT(&rbufp->recv_srcadr) < NTP_PORT) {
+ if (SRCPORT(&rbufp->recv_srcadr) == 0) {
sys_badlength++;
return; /* bogus port */
}