Cyber-Criminals Target Another Network Service to Amplify DDoS Attacks

Level3 finds cyber-attackers are increasingly abusing another common network service known as portmap, or portmapper, to amplify their attacks.

DDoS Amplification 2

Attackers have started using a common network service to amplify Distributed Denial-of-Service attacks and flood targeted networks with data packets, telecommunications firm Level 3 Communications stated in an analysis published on Aug. 17.

Using the service, known as portmap or portmapper, an attacker can send a simple request and create a much larger stream of data—from 7 to 28 times larger—to be sent to a targeted network.

Since June, the number of attacks using portmapper has increased by a factor of 22, and even though the number of attacks continues to be small, the trend suggests that attackers may be switching to the new technique, Level 3 researchers stated in their analysis.

"We caught this early on," Dale Drew, chief security officer for Level 3 Communications, told eWEEK. "We caught these bad guys experimenting, and it looks like they were developing code, automating the attack and make it easier to run."

Denial-of-service attacks often use a technique called amplification to make a small attack into a much bigger flood of data. In an amplification attack, a single network packet is sent to a server running a vulnerable service, causing the server to respond with a much large volume of data. The attack essentially uses legitimate, but vulnerable, Internet infrastructure to attack a target.

In the latest case, attackers are using portmapper—a service that tracks which logical "ports" on a computer allow access to specific applications—to magnify a 50- to 80-byte request by a factor of 7 to 28 times. Level 3 has witnessed attacks amplified by a factor of nearly 20.

The company is not the only one to detect novel ways of amplifying denial-of-service attacks. Security firms have seen a steady stream of new techniques over the past few years.

The computers used to keep time synchronized across the Internet, known as network time protocol (NTP) servers, were commonly used by attackers in 2013 and early 2014 to magnify attack traffic.

Starting in late fall 2014, attackers focused on another communications method, the Simple Service Discovery Protocol (SSDP), which is used by Universal Plug-and-Play devices (UPnP) devices to automatically configure themselves. And, earlier this year, attackers used an older protocol, known as the Routing Information Protocol version 1 (RIPv1), to amplify their attacks.

Level 3's data suggests that there are a million servers exposing the portmapper service on the Internet that could be used in an amplified attack, said CSO Drew. In the past, some of the largest attacks seen by security firms were caused by NTP amplification, and Drew worries that, using portmapper, a similar threat could emerge.

Because criminals use denial-of-service attacks as a way to extort cash from online businesses, constantly coming up with new ways around defensive technologies is important for them. Already, online-gaming companies and Web-hosting firms have been hit with a handful of attacks using the technique, Drew said.

"What we are seeing is that these criminals are looking to make a tremendous amount of money using DDoS extortion attempts," he said.

Robert Lemos

Robert Lemos

Robert Lemos is an award-winning freelance journalist who has covered information security, cybercrime and technology's impact on society for almost two decades. A former research engineer, he's...