DNS FLood Detector 1.2
Dennis Opacki
dopacki@adotout.com
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:
http://www.caida.org/tools/visualization/plot-latlong/
How do I build it?
Execute ./configure.pl to select the appropriate make target. Then simply
type “make”.
Why was it written?
I wrote DNS Flood Detector because the fifty or so public recursive
nameservers I am responsible for were being abused by both customers and
non-customers. DNS Flood Detector allows for prompt action when anomalous
conditions are detected.
What do I need to use it?
You need libpcap and a little bit of patience.
What platforms does it work on?
Linux, BSDI, FreeBSD, Mac OSX, Solaris
Will it run under Windows {95,98,NT,2000,XP,2003,2008 or Win7}?
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 226.1.1.2)
-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 [192.168.1.45] – 0 qps tcp : 24 qps udp [8 qps A] [16 qps PTR]
[15:14:56] source [10.0.24.2] – 0 qps tcp : 15 qps udp [15 qps A]
[15:15:06] source [192.168.1.45] – 0 qps tcp : 24 qps udp [8 qps A] [16 qps PTR]
[15:15:06] source [10.0.24.2] – 0 qps tcp : 15 qps udp [14 qps A]
[15:15:16] source [192.168.1.45] – 0 qps tcp : 23 qps udp [7 qps A] [15 qps PTR]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [113.96.236.11] – 0 tcp qps : 153 udp qps [151 qps A] [1 qps MX] [2 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [117.185.251.211] – 0 tcp qps : 22 udp qps [20 qps A] [1 qps MX] [2 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [117.185.251.192] – 0 tcp qps : 63 udp qps [57 qps A] [1 qps MX] [5 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [113.96.17.165] – 0 tcp qps : 102 udp qps [100 qps A] [1 qps MX] [2 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [58.60.10.12] – 0 tcp qps : 109 udp qps [107 qps A] [1 qps MX] [2 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [120.204.17.12] – 0 tcp qps : 155 udp qps [154 qps A] [1 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [120.204.17.67] – 0 tcp qps : 82 udp qps [81 qps A] [1 qps MX] [2 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [223.167.253.12] – 0 tcp qps : 59 udp qps [57 qps A] [1 qps MX] [2 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [47.252.82.250] – 1 tcp qps : 76 udp qps [76 qps A] [1 qps AAAA]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [120.204.20.12] – 0 tcp qps : 40 udp qps [40 qps A] [1 qps MX]
Feb 15 16:59:05 ns1-bd dns_flood_detector[21585]: source [112.65.192.108] – 0 tcp qps : 38 udp qps [37 qps A] [1 qps MX] [1 qps AAAA]
结合fail2ban
failregex = .* dns_flood_detector\[\d+\]: source \[<HOST>\].* \d{3,}.* (tcp|udp) qps.*
可以拦截特定IP的大量请求