DNS Flood Detector 1.20 (NEW for 2012!)
by Dennis Opacki

What is DNS Flood Detector?
DNS Flood Detector was developed to detect abusive usage levels on high traffic nameservers and to enable quick response to the use of one's nameserver to facilitate spam. DNS Flood Detector is distributed under the Gnu Public License (see included LICENSE file for details).

How does it work?
DNS Flood Detector uses libpcap (in non-promiscuous mode) to monitor incoming dns queries to a nameserver. The tool may be run in one of two modes, either daemon mode or "bindsnap" mode. In daemon mode, the tool will alarm via syslog. In bindsnap mode, the user is able to get near-real-time stats on usage to aid in more detailed troubleshooting. By default, it will count dns queries directed to any address in the same network as the primary IP address on the interface being watched; the -A, -M, and -Q options can be used to modify this behaviour.

As of version 1.2, DNS Flood Detector can now send source IP request data to a network-based collector as JSON. This lets you gather near real-time information about who is using your DNS servers, and from where. I've included a sample application called dns_flood_collector.pl, which you can use to receive and report these data. The output of this program can be easily fed into a graphing tool, such as Caida's plot-latlong:


Why was it written?
I wrote DNS Flood Detector because the fifty or so public recursive nameservers I was responsible for were being abused by both customers and non-customers. DNS Flood Detector allowed for prompt action when anomalous conditions were detected.

Thank you Jim and Erik for your patches and troubleshooting; you have helped make DNS Flood Detector a more useful tool for the Internet community!

What do I need to use it?
You need libpcap and a little bit of patience. I have currently tested DNS Flood Detector on Linux, OSX, BSDI, Solaris 9, and FreeBSD.

Will it run under Windows {95,98,ME,NT,2000,XP}?
Maybe. I haven't tried. If it doesn't, feel free to submit a fix.

What does it look like?

Usage: ./dns_flood_detector [OPTION]

-i IFNAME              specify interface to listen on
-t N                   alarm at >N queries per second
-a N                   reset alarm after N seconds
-w N                   calculate stats every N seconds
-x N                   create N buckets
-m N                   mark total query rate every N seconds
-A addr                filter for specific address
-M mask                netmask for filter (in conjunction with -A)
-Q                     don't filter by local interface address
-b                     run in foreground in bindsnap mode
-d                     run in background in daemon mode
-D                     dump dns packets (implies -b)
-v                     verbose output - use again for more verbosity
-s                     send source IP stats to collector as JSON
-z N.N.N.N             address to send stats to (default
-p N                   UDP port to send stats to (default 2000)
-h                     display this usage information

Sample Output:

dopacki:~$ sudo ./dns_flood_detector -v -v -b -t10
[15:14:56] source [] - 0 qps tcp : 24 qps udp [8 qps A] [16 qps PTR] 
[15:14:56] source [] - 0 qps tcp : 15 qps udp [15 qps A] 
[15:15:06] source [] - 0 qps tcp : 24 qps udp [8 qps A] [16 qps PTR] 
[15:15:06] source [] - 0 qps tcp : 15 qps udp [14 qps A] 
[15:15:16] source [] - 0 qps tcp : 23 qps udp [7 qps A] [15 qps PTR] 

Where do I get it?

Right here, of course!
Download current version (1.20) of dnsflood.tgz

Thanks to Larry Long for the RPM and SRPM packages (1.08 at the moment).

What if I have questions?
You can e-mail me at dopacki@adotout.com

Want to know more about me?
Dennis's resume (PDF)

Links to other projects of mine
Trust Informations - security metrics service
Let's Talk About Risk [Paper - 2007]
Business Case for Information Assurance Invetment [ Causal Loop Diagram - 2006]
Security Metrics: Building Business Unit Scorecards [Paper - 2005]
Exploring Anonymous Networking: MIT's Tor Project [Paper - 2004]
IP Flood Detector v1.0 (detect TCP,UDP and ICMP packet floods)
Echoart v0.1 (ASCII art over ICMP)
Netmatrix v0.2 (network monitoring)
Disconnect.cgi (Cisco RAS management)
Decoy email link