Distributed denial-of-service (DDoS) attacks remain a popular attack vector but have undergone changes as cybercriminals shift their strategies. Today's attackers are turning to mobile and Internet of Things (IoT) technologies to diversify and strengthen their DDoS campaigns, research shows.
Researchers with A10 Networks, which tracked nearly 6 million DDoS weapons in the fourth quarter of 2019, today published "DDoS Weapons and Attack Vectors" to share the trends in today's DDoS landscape. These include the weapons being used, locations where attacks are launched, services exploited, and techniques attackers are using to maximize damage caused.
DDoS weapons are distributed around the world; however, the bulk of attacks start in countries with the most Internet connectivity. China is the origin of the highest number of DDoS attacks, with 739,223 starting in the country. The United States is second, with 448,169, followed by the Republic of Korea (440,185), India (268,864), Russia (253,609), and Taiwan (199,656).
The SNMP and SSDP protocols, long the top sources for DDoS attacks, continued to take the top spots in the fourth quarter with nearly 1.4 million SNMP weapons and nearly 1.2 million SSDP weapons tracked. The next one was a surprise: Researchers saw a sharp spike in attacks using WD-Discovery; these rose to nearly 800,000 to become the third most common source of DDoS.
A10 Networks attributes this change to the growing popularity of attackers leveraging misconfigured IoT devices to amplify their campaigns. As part of this trend, called "reflected amplification," attackers are focusing on the rising number of Internet-exposed IoT devices running the WS-Discovery protocol. WD-Discovery, a multicast UDP-based communications protocol, is used to automatically detect Internet-connected services. It's used in many devices, going back to Windows Vista; video encoders, printers, cameras, DVRs, and some on-prem security systems reply back to researchers' WS-Discovery Internet scans.
WD-Discovery does not perform IP source validation, researchers note, so it's easy for attackers to spoof a victim's IP address. Doing this resulted in the victim being flooded with data from nearby IoT devices, they say.
"The reason WS-Discovery has been of a particular interest is not just its ability to generate a large attack but depending on the contents of the query sent by the attacker to the amplification system, the customer could be hit with an attack that conventional methods, such as those at layer 3 and layer 4, they cannot fully protect themselves from," explains Rich Groves, director of R&D at A10 Networks. This is why he considers both SSDP and WS Discovery as more dangerous than other DDoS attack sources.
Reflected amplification has been "highly effective," they note, with more than 800,000 WS-Directory hosts available to exploit and observed amplification reaching 95x. These attacks have reached a massive scale and account for the majority of DDoS attacks, researchers say. Most inventory has been found in Vietnam, Brazil, the US, the Republic of Korea, and China.
As more IoT devices connect to the Internet, and the growth of 5G drives network speed and coverage, researchers anticipate attackers will continue to find ways to leverage the IoT. DDoS-for-hire services will make it even simpler for any attacker to launch a destructive attack.
"Attackers are good at figuring out which countermeasures are in place and which are not, especially Booter systems, as they are compelled to be better than their competitors," says Groves. "Filters for some attacks are deployed throughout the Internet all of the time and some are much harder to accomplish." WS-Discovery is especially challenging, he continues, as a portion of the traffic is sourced from a common but high source port (UDP 3702) and sometimes the rest of the layer 4 signature is random (random high UDP ports). Service proviers usually don't want to block traffic sourced from high UDP ports because of the potential for collateral damage, he adds. This gives attackers a gap in the perimeter to strike.
DDoS is also going mobile, researchers found. As an example, Groves points to the large number of Android systems with an unprotected diagnostics backdoor. "This is actively being used to place Mirai-like malware on the phone to make it a weapon," he explains. Further, attackers are widely deploying protocols such as COAP, which unlike the backdoor for Android, is an amplification vector that works similarly to WS-Discovery.
The popularity of DDoS weapons hosted by mobile carriers "skyrocketed" toward the end of 2019, researchers found. The top-reflected amplified source for DDoS attacks, they noticed, was Guangdong Mobile Communication Co. Brazilian mobile company Claro was a top source of malware-infected drones.
They also looked at trends around autonomous number systems (ASNs), or collections of IP address ranges under a single entity or government, hosting DDoS weapons. The top ASNs hosting DDoS weapons also included Guangdong Mobile Communication Co. and Chinanet, as well as Korea Telecom, aligning with countries that also host a high number of DDoS attacks.
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