Cybercriminals are increasingly targeting corporate networks, websites, and online services with low-bandwidth distributed denial-of-service (DDoS) attacks that exploit weaknesses in application infrastructure to disrupt business, Internet infrastructure firm Neustar stated in an August 14 threat report.

In its "Q2 2019 Cyberthreats & Trends" report, Neustar found that DDoS attacks using less than 5 Gbit/s make up a greater share of packet floods, with more than 75% of all attacks using less than 5 Gbit/s in the second quarter of 2019, up from less than 70% the previous year. The average attack consisted of a 0.99 Gbit/s stream of packets, so small that most companies may not notice the impact, says Michael Kaczmarek, vice president of product for Neustar Security.

"People think DDoS is going away," he says. "They think it is this unsophisticated brute-force attack, but by no means is it gone; it has just morphed."

Overall, DDoS attacks increased by 133%, more than doubling, according to Neustar's report. The trend is a reversal from last year, when security firms had documented a decrease in attacks for most of the year. The average attack also showed greater complexity, with 82% of attacks using two or more different threat vectors.

The different vectors aim to find a vulnerable spot in a company's infrastructure and abuse the weakness, Kaczmarek says.

"The attackers are getting more sophisticated in what they are targeting," he says. "They are going after not the most vulnerably guy, but the most vulnerable component of the infrastructure."

Most companies seem to have a pretty good response to attacks, however, with a quarter initiating DDoS mitigation within a minute and another 62% within five minutes. Only 11% of companies actually take longer than 5 minutes to respond to a DDoS attack.

In addition, companies are likely to detect multivector attacks, with only 14% of firms very unlikely or somewhat unlikely to notice smaller attacks.

Neustar argues in the report, however, that any response aside from "very likely to detect a smaller attack" is a security failure. "Fewer than 3 in 10 organizations are very likely to notice smaller multi vector attacks, suggesting that greater awareness would be beneficial," the company states in the report.

The study raises questions about what exactly can be defined as a distributed denial-of-service attack. The inclusion of much smaller attacks, of which seven in 10 companies are not certain to detect, suggests that DDoS attacks are merging with the standard tactic of scanning for vulnerabilities in security companies' lexicons. (The report appears to use a standard definition of DDoS as an attack that denies service.)

"The basic form and composition of the DDoS traffic may not have changed much, but the ability to precisely target these attacks has evolved markedly," the report states. "DDoS attacks can now be directed at specific services, gateways, applications, and Application Programming Interfaces (API), and as the target becomes smaller, less traffic is required to bring it down."

Most companies would likely, however, detect an interruption of service to some part of their infrastructure. Most of these attacks fall in the area of application-layer attacks, and not just denial of service, according to Kaczmarek, who included both credential-stuffing and SQL injection scans as potential examples.

"It could be the attack is targeting a specific resource that you were not aware of," he says. "It could be a billing app that is out there, or an API that is doing a communication between you and the bank. [Finding these attacks is] going to require a deeper investigation."

The upshot is that attackers are no longer focused on just denying service but on a range of goals that can be accomplished with scans, packet floods, and application attacks. For that reason, Internet infrastructure-security companies have followed suit with defenses.

"It goes back to the idea of what is valuable versus what is vulnerable," Kaczmarek says. "I may not notice these attacks immediately, but in the end, even the smaller ones will have a large impact overall."