Tuesday, August 9, 2022

DDoS detection with advanced real-time flow analytics

The diagram shows two high bandwidth flows of traffic to the Customer Network, the first (shown in blue) is a bulk transfer of data to a big data application, and the second (shown in red) is a distributed denial of service (DDoS) attack in which large numbers of compromised hosts attempt to flood the link connecting the Customer Network to the upstream Transit Provider. Industry standard sFlow telemetry from the customer router streams to an instance of the sFlow-RT real-time analytics engine which is programmed to detect (and mitigate) the DDoS attack.

This article builds on the Docker testbed to demonstrate how advanced flow analytics can be used to separate the two types of traffic and detect the DDoS attack.

docker run --rm -d -e "COLLECTOR=host.docker.internal" -e "SAMPLING=100" \
--net=host -v /var/run/docker.sock:/var/run/docker.sock:ro \
--name=host-sflow sflow/host-sflow
First, start a Host sFlow agent using the pre-built sflow/host-sflow image to generate the sFlow telemetry that would stream from the switches and routers in a production deployment. 
setFlow('ddos_amplification', {
  value: 'frames',
  values: ['count:ipsource']
setThreshold('ddos_amplification', {
  value: 10000,
  timeout: 2
setEventHandler(function(event) {
  var [ipdestination,udpsourceport] = event.flowKey.split(',');
  var [sourcecount] = event.values;
  if(sourcecount === 1) {
    logInfo("bulk transfer to " + ipdestination);
  } else {
    logInfo("DDoS port " + udpsourceport + " against " + ipdestination);
The ddos.js script above provides a simple demonstration of sFlow-RT's advanced flow analytics. The setFlow() function defines the a flow signature for detecting UDP amplification attacks, identifying the targetted IP address and the amplification protocol. In addition to the primary value of frames per second, a secondary value counting the number of ipsource addresses has been included. The setThreshold() function causes an event to by generated whenever a flow exceeds 10,000 frames per second. Finally, the setEventHandler() function defines how the events will be processed. See Writing Applications for more information on developing sFlow-RT applications.
docker run --rm -v $PWD/ddos.js:/sflow-rt/ddos.js \
-p 8008:8008 -p 6343:6343/udp --name sflow-rt \
sflow/prometheus -Dscript.file=ddos.js
Start sFlow-RT using pre-built sflow/prometheus image.
docker run --rm -it sflow/hping3 --flood --udp -k \
-p 443 host.docker.internal
In a separate window, simulate a bulk tranfer using pre-built sflow/hping3 image (use CTL+C to stop the attack).
2022-08-09T00:03:20Z INFO: bulk transfer to
The transfer will be immediately detected and logged in the sFlow-RT window.
docker run --rm -it sflow/hping3 --flood --udp -k \
--rand-source -s 53 host.docker.internal
Simulate a UDP amplification attack.
2022-08-09T00:05:19Z INFO: DDoS port 53 against
The attack will be immmediately detected and logged in the sFlow-RT window.

The open source sFlow-RT ddos-protect application is a full featured DDoS mitigation solution that uses the advanced flow analytics features described in this article to detect a wide range of volumetric attacks. In addition, ddos-protect can automatically mitigate attacks using BGP remotely triggered blackhole (RTBH) or BGP Flowspec actions. DDoS protection quickstart guide describes how to test, deploy, and monitor the DDoS mitigation solution with examples using Arista, Cisco, and Juniper routers.

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