FreeBSD Security Advisory - If ntpd receives a mode 7 (MODE_PRIVATE) request or error response from a source address not listed in either a 'restrict ... noquery' or a 'restrict ... ignore' section it will log the even and send a mode 7 error response. If an attacker can spoof such a packet from a source IP of an affected ntpd to the same or a different affected ntpd, the host(s) will endlessly send error responses to each other and log each event, consuming network bandwidth, CPU and possibly disk space.
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