Distributed denial-of-service attacks (DDoS) — particularly those lasting more than an hour — increased sharply in number during the first quarter of this year over the prior quarter after declining steadily for most of 2018.
The unexpected resurgence suggests that new suppliers of DDoS services have quietly emerged to replace operators that were disrupted in a series of law enforcement actions last year, Kaspersky Lab said in a report summarizing DDoS activity in Q1 2019.
The security vendor's analysis shows the number of DDoS attacks in Q1 to be some 84% higher than the number recorded in the last three months of 2018.
One significant trend that Kaspersky Lab notes is an overall increase in the number of attacks lasting one hour or longer. Over one in 10 (10.13%) of the DDoS attacks in Kaspersky Lab's dataset lasted between five hours and nine hours, and another 9.37% lasted between 10 hours and 49 hours — or more than two days. Some 2% of the attacks were longer than 50 hours, with the longest one lasting 289 hours, or just over 12 days.
In total, the proportion of sustained attacks, or those lasting more than an hour, nearly doubled from 11% of the overall number of DDoS attacks in the last quarter of 2018 to 21% of the total in the first three months this year. Correspondingly, the number of short-duration DDoS attacks lasting less than four hours declined — from 83.34% in Q4 2018 to 78.66% this year.
Alexander Gutnikov, an analyst with Kaspersky Lab DDoS prevention service, says attackers are increasingly moving away from volumetric, high-bandwidth attacks at the network (L3) and transport (L4) layers because of the mitigations available for such attacks. Instead, they are turning to smarter DDoS attacks such as those that target the application layer.
"The main driver of the growth of smart DDoS attacks is a decrease in the effectiveness of volumetric attacks," Gutnikov says. "Volumetric attacks have to be very powerful to significantly affect the stability of resources," For vendors that provide dedicated DDoS mitigation services, the trend is not particularly new. he adds.
As has been the case for several years, a majority of DDoS attacks last quarter were SYN flood attacks. However, the number of SYN attacks as a percentage of the overall total of DDoS attacks jumped sharply from 58.1% in the last quarter of 2018 to over 84% in this year's first quarter. Meanwhile, other types of DDoS attacks, such as UDP flooding and TCP flooding, showed a corresponding decrease.
HTTP flooding attacks targeting the Web application layer are still relatively rare. However, the number of such attacks appears to be growing. Kaspersky Lab analysis shows HTTP flood attacks increasing in number from 2.2% of the overall total in Q4 to 3.3% last quarter. "In terms of the ratio of effectiveness and cost of organization, application-level attacks, L7, are an optimal option for malefactors," Gutnikov notes.
A Persistent Threat
Kaspersky Lab's new report is the latest to highlight the continuing threat that DDoS attacks present to organizations despite some major wins for law enforcement against those behind such attacks.
Last April, for instance, European law enforcement agencies, in cooperation with their counterparts in other regions of the world, dismantled Webstresser, one of the largest sites for buying and selling DDoS services at the time, and announced the arrests of the operators and several clients of the illegal outfit.
More recently the US Justice Department announced it had seized 15 websites offering similar DDoS-for-hire services and charged three individuals for their roles in the operation. In January, a Boston federal judge sentenced an individual convicted on charges of launching a DDoS attack on Boston Children's Hospital to 10 years in prison.
The fact that the number of attacks increased last quarter are all the same suggests that new actors have stepped up to the plate to replace the old operators, according to Kaspersky Lab.
"We believe that the motives for DDoS services remain the same: politics, unfair competition, concealment of other cybercrime, or personal motives," Gutnikov says. "And for people who conduct DDoS attacks, the main motive is money."
Data from Verizon's "2019 Data Breach Investigations Report" (DBIR) shows that public-sector organizations and those in the IT, finance, and professional services sectors are far more frequent targets of DDoS attacks than organizations in other industries. Verizon counted more than 990 DDoS incidents against public-sector organizations in 2018, 684 attacks against IT organizations, 575 targeting financial firms, and nearly 410 against professional services firms.
Financial services organizations and IT companies are also targets of some of the biggest DDoS attacks — from a bandwidth and packets-per-second standpoint. Verizon's data shows that in 2018, the median size of DDoS attacks against financial services companies and IT organizations were 1.47 Gbps and 1.27 Gbps, respectively.
"Over time, DDoS attacks have been getting much more tightly clumped with regard to size," with little difference in size between the largest and smallest attacks, Verizon said.
Ominously for enterprise organizations, while DDoS attacks, on average, have shrunk in size overall, there has been an increase in the number of really massive attacks.
According to security vendor Imperva, there has been a recent increase in DDoS attacks involving 500 million or more attack packets per second. During a one-week period earlier this year, Imperva's researchers detected nine such DDoS attacks, with the largest one hitting an astounding 652 million packets per second.
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