Cybercrooks shift tactics in DDoS attacks, researchers say

The shuddering effectiveness of the DNS reflection DDoS attack on Spamhaus in March is a forewarning of a growing criminal interest in the technique, new figures from mitigation firm Prolexic have suggested.

Using Prolexic's customers for measurement, in the third quarter of 2013 year-on-year the number of attacks increased by 58 percent over the same period in 2012 while attack duration went up 13.3 percent. This made the quarter a record-breaking high for any three-month period. But as ever with this category of security threat, the real story was the change in the type of attacks.

For instance, infrastructure layer attacks went up 48 percent while application layer attacks doubled, which suggests less focus on simple traffic bombardment as mitigation services get on top of this type of hazard.

The most intriguing story was the sudden rise of 'Distributed Reflection Denial of Service' (DrDoS) attacks of the sort used against Spamhaus, something Prolexic believes is being driven by a range of factors starting with the fact that criminals are now trading lists of vulnerable servers to use in such assaults. The relative success of high-profile reflection attacks had also caused this modus operandi to be included in DDoS-as-a-service attack tools.

"This quarter, the major concern is that reflection attacks are accelerating dramatically, increasing 265 percent over Q3 2012 and up 70 percent over Q2," suggested Prolexic president, Stuart Scholly. "The bottom line is that DDoS attackers have found an easier, more efficient way to launch high bandwidth attacks with smaller botnets and that's concerning."

Another attraction of DrDoS attacks was that they afforded a degree of anonymity, he said. The hijacking of intermediaries to amplify the effect meant that this design created two victims, the intended target and the intermediary.

"Prolexic believes the adoption of DrDoS attacks is likely to continue, as fewer bots are required to generate high volumes of attack traffic due to reflection and amplification techniques," agreed the report authors.

A popular target for DrDoS attack was the global gambling industry while the overwhelming majority of attacks recorded by Prolexic customers—about 62 percent—were directed from (or at least through) China.

Longer term, the economics of DDoS remained firmly on the side of the attackers because it costs far less to launch an attack than to defend against one. In order to head off a widening of this gap, the industry should look to retire obsolete and obscure protocols such as 'Chargen', a network test protocol widely abused in DrDoS attacks as well as tackle the money channels used to sell DDoS-for-hire services.

Rival mitigation firm Arbor Network last week announced its own cut on the first three quarters of 2013, reporting a rise in the number of very large attacks breaching the 20Gbps threshold. Arbor also announced a collaboration with Google to visualize global DDoS trends using graphs designed by the search giant.

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