What is a DNS reflection amplification attack?
A DNS reflection attack, also known as a DNS amplification attack, is a type of DDoS attack that exploits open DNS servers to amplify the volume of traffic directed towards a target. A DNS reflection attack is conducted by using spoofed IP addresses to overwhelm a DNS server. Attackers achieve this amplification by sending forged DNS queries to open DNS servers, which in turn respond with larger DNS responses to the victim’s IP address. This results in overwhelming the victim’s network or server with a high volume of traffic, leading to service disruption or denial of service.
See also: cyberattack, DNS attack, DNS server, DNS cache
Reflection amplification attack protection
- Robust DNS server security. Good practices to create a strong security system for DNS servers include DNS activity logging, keeping the DNS cache locked, separating authoritative from recursive name servers, monitoring the DNS server closely and updating it frequently.
- Block certain DNS servers. A list of suspicious DNS servers can be created to prevent DNS reflection attacks. If there is no information on which DNS servers are suspicious, all open recursive relay servers can be simply blocked instead.
- Response Rate Limiting. Response Rate Limiting (RRL) is a mitigation tool used to protect DNS servers from DNS amplification attacks.
Why are reflection amplification attacks dangerous?
Reflection amplification attacks pose significant threats to network security for several reasons:
- Increased attack volume: These attacks can generate a massive volume of traffic directed at the target by exploiting vulnerable servers. This amplification effect allows attackers to overwhelm a target with relatively small initial requests, making it difficult for the target to respond.
- Difficult to trace: Since the attack traffic is sent from legitimate servers that the attacker has exploited, it can be challenging to trace the source of the attack. This obfuscation complicates mitigation efforts and allows attackers to evade detection.
- Service disruption: Reflection amplification attacks can lead to prolonged service outages for targeted organizations. This disruption can result in financial losses, reputational damage, and diminished customer trust.
- Resource consumption: Such attacks consume bandwidth and server resources, affecting not only the target but also the intermediary servers used in the attack. This can lead to cascading effects, impacting overall network performance and availability.
DNS reflection amplification examples
Here are some notable examples of DNS reflection amplification attacks:
- 2000 Mafiaboy attack: A teenager, known as Mafiaboy, took down major sites like CNN and eBay by exploiting DNS servers, flooding them with traffic.
- 2014 Spamhaus attack: Targeting the anti-spam organization Spamhaus, attackers generated 300 Gbps of traffic, causing widespread internet slowdowns by amplifying DNS requests.
- 2018 Google Services attack: Attackers used DNS amplification to peak at over 2.54 Tbps, disrupting Google's services and demonstrating the attack's massive scale.
- 2020 New Zealand Exchange attack: This attack disrupted trading services on the New Zealand Stock Exchange, highlighting the vulnerabilities of critical infrastructure to DNS amplification techniques.
These incidents illustrate the serious risks associated with DNS reflection amplification attacks.
