What are DNS Amplification Attacks
DNS amplification attacks are a version of distributed denial-of-service attacks (also known as DDoS). These DNS amplification attacks use DNS servers as amplifiers.
The attack itself is rather simple: the attacker has their botnet send tens of thousands of DNS requests to one or more public DNS resolvers. The bots use the target’s IP address as sender IP so that the DNS resolver’s replies are sent to the target instead of the attacker. That way, the DNS resolvers submit tens of thousands of replies to the target.
This is what the communication structure looks like (the example has just one bot attacking):
The attacker also exploits a specific feature of the DNS protocol: requests directed to DNS servers are often much smaller than their replies. A request with just a few bytes can trigger a reply with thousands of bytes. For example, a 50-byte request can result in a 5000-byte reply – an amplification factor of 100. This means that the attacker need only send a fraction of the data volume that is supposed to hit their target. A bot with a bandwidth of 10 Mbps can run an attack on the order of 1 Gbps, and an entire botnet can easily reach hundreds of Gbps.
Even a simple request for an A record with a packet size of 74 bytes can lead to a 508-byte reply (an amplification factor of approximately 7). A request and reply like this might look as follows (no layer-2 and layer-3 header shown):
- Request from client (IP A.B.C.D) to DNS resolver (IP Q.W.E.R) for “www.thefqdn.de”, packet size of 74 bytes (©Link11)
This is what the botnet communication looks like including amplification:
The target faces several threats:
- Internet connection overload
- Overload of the components processing the packets
The worst possible outcome of this type of attack is complete failure of the target’s internet connection.
Stay updated on current DDoS reports, warnings, and news about IT security, cybercrime and DDoS protection.
Follow Link11 on Twitter
The gaming and gambling industries are under attack. As a huge market that relies on the internet, they are a highl…
3 Retweets 1Read More
Recent data from Link11 shows that the second quarter of 2019 saw a 97 percent year-on-year increase in average att…
6 Retweets 3Read More
RTL Germany Media Group’s production, broadcast and IT company CBC has switched from ad hoc protection to the perma…
3 Retweets 3Read More
We have seen some alarming trends over the last year in the DDoS threat landscape. 2 in 3 DDoS attacks used multipl…
5 Retweets 3Read More
DDoS attacks increased 97% year-on-year in average attack bandwidth in Q2 2019. Visit our blog to see the full info…
5 Retweets 3Read More