This Module monitors DNS servers and DNS traffic as follows:
It calculates an average DNS servers’ response time over a specified time interval and reports it for all observed DNS servers
It calculates an average DNS servers’ packet size (both in and out). DNS attacks are characterized by suspiciously large messages (packet size over 512 bytes)
It reports top DNS users
DNS users are reported by DNS Users Monitor Module (10005,20005)
Data Collection Interval, sec
Module logic execution interval
min = 30 sec, max = 600 sec, default = 60 sec
NetFlow v5, v9, and IPFIX. Cisco ASA NSEL is not fully supported by this Module. Please contact [email protected] for more information.
Required NetFlow Fields
Information Element (IE)
IE size, B
The IPv4 source address in the IP packet header
The IPv4 destination address in the IP packet header
The value of the protocol number in the IP packet header. The protocol number identifies the IP packet payload type. Protocol numbers are defined in the IANA Protocol Numbers registry.
The source port identifier in the transport header. For the transport protocols UDP, TCP, and SCTP, this is the source port number given in the respective header.
The destination port identifier in the transport header. For the transport protocols UDP, TCP, and SCTP, this is the destination port number given in the respective header.
4 or 8
The number of octets since the previous report (if any) in incoming packets for this Flow at the Observation Point. The number of octets includes IP header(s) and IP payload.
4 or 8
The number of incoming packets since the previous report (if any) for this Flow at the Observation Point.
The relative timestamp of the first packet of this Flow. It indicates the number of milliseconds since the last (re-)initialization of the IPFIX Device (sysUpTime). sysUpTime can be calculated from systemInitTimeMilliseconds.
The relative timestamp of the last packet of this Flow. It indicates the number of milliseconds since the last (re-)initialization of the IPFIX Device (sysUpTime). sysUpTime can be calculated from systemInitTimeMilliseconds.
Syslog/JSON Message Fields – Average DNS response time
Message type identifier
NetFlow exporter IP address
Transport Protocol (TCP = 6, UDP = 17)
DNS server IPv4 address
Destination host name
<string>, included when FQDN is on
Min DNS server response time, msec
Max DNS server response time, msec
DNS server average response time, msec
Number of flows
Average packet size received by the host from DNS server
Packets received by the host from DNS server
Average packet size sent by the source host to DNS server
Packets sent by the source host DNS server, packets
Observation time interval, msec
(1) Host name field is optional and included only if FQDN Service is enabled