Loop DoS: New Denial-of-Service Attack targets Application-Layer Protocols

Illustration "Application-Layer Loop DoS Attacks"
(c) CISPA

A new Denial-of-Service (DoS) attack targets application-layer protocols that draw on the User Datagram Protocol (UDP) for end-to-end communication. ‘Application-layer Loop DoS Attacks’ pair servers of these protocols in such a way that they communicate with each other indefinitely. The vulnerability affects both legacy (e.g., QOTD, Chargen, Echo) and contemporary (e.g., DNS, NTP, and TFTP) protocols. Discovered by researchers of the CISPA Helmholtz-Center for Information Security, the attack puts an estimated 300,000 Internet hosts and their networks at risk.

The newly discovered DoS loop attack is self-perpetuating and targets application-layer messages. It pairs two network services in such a way that they keep responding to one another’s messages indefinitely. In doing so, they create large volumes of traffic that result in a denial of service for involved systems or networks. Once a trigger is injected and the loop set in motion, even the attackers are unable to stop the attack. Previously known loop attacks occurred on the routing layer of a single network and were limited to a finite number of loop iterations.

An estimated 300,000 Internet hosts can be abused

Discovered by CISPA researchers Yepeng Pan and Professor Dr. Christian Rossow, application-layer loop DoS attacks are likely to concern a total of 300,000 Internet hosts. So far, Pan and Rossow have confirmed vulnerabilities for TFTP, DNS and NTP implementations as well as for the six legacy protocols Daytime, Time, Active Users, Echo, Chargen and QOTD. These protocols are widely used to provide basic functionalities on the Internet. While NTP, for instance, allows for time synchronization between computers, DNS matches domain names to their corresponding IP addresses. TFTP enables the transmission of files without user authentication.

Attacks can be triggered from a single spoofing-capable host

Application-layer loop DoS attacks rely on IP spoofing and can be triggered from a single spoofing-capable host. “For instance, attackers could cause a loop involving two faulty TFTP servers by injecting one single, IP-spoofed error message. The vulnerable servers would then continue to send each other TFTP error messages, putting stress on both servers and on any network link between them”, Rossow explains. Pan stresses the novelty of this attack vector: “The application-level loops we discovered differ from known network-layer loops. Hence, existing packet lifetime checks employed at the network level are unable to interrupt application-layer loops.”

Easy to exploit

“As far as we know, this kind of attack has not yet been carried out in the field. It would, however, be easy for attackers to exploit this vulnerability if no action were taken to mitigate the risk”, Rossow says. In December 2023, Rossow and Pan disclosed their discovery to the affected vendors and a trusted operator community. The two CISPA researchers coordinated a plan for the publication of an attack-specific advisory and started a notification campaign together with The Shadowserver Foundation.

Starting March 19, 2024, the attack specific advisory will be accessible via https://cispa.saarland/group/rossow/Loop-DoS

Wissenschaftliche Ansprechpartner:

Prof. Dr. Christian Rossow
rossow@cispa.de
https://cispa.de/en/people/rossow

https://cispa.de/en/loop-dos

Media Contact

Eva Michely Unternehmenskommunikation
CISPA Helmholtz Center for Information Security

All latest news from the category: Information Technology

Here you can find a summary of innovations in the fields of information and data processing and up-to-date developments on IT equipment and hardware.

This area covers topics such as IT services, IT architectures, IT management and telecommunications.

Back to home

Comments (0)

Write a comment

Newest articles

ispace and University of Leicester collaborate on lunar night survival technology

ispace, inc. (ispace), a global lunar exploration company, and the University of Leicester, have agreed to collaborate on approaches to lunar night survivability for future ispace lunar lander and rover…

Technique to analyze RNA structures in ultra-high definition

This is where the Nottingham team, led by Dr Aditi Borkar, Assistant Professor in Molecular Biochemistry & Biophysics in the School of Veterinary Medicine and Science, has achieved a transformative…

Iron could be key to less expensive, greener lithium-ion batteries

What if a common element rather than scarce, expensive ones was a key component in electric car batteries? A collaboration co-led by an Oregon State University chemistry researcher is hoping…

Partners & Sponsors