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ICANN freezes over fast flux fury

Botnet deadlock

The non-profit group that oversees the internet's address system is seeking the public's help in deciding what to do about the growing use of a technology known as fast flux, which is used by cybercriminals to thwart take-down efforts, but which can also be used for legitimate purposes as well.

The Internet Corporation for Assigned Names and Numbers (ICANN) opened a 20-day comment period on Monday, the same day its Working Group on Fast Flux issued a report saying, essentially, that its members are deadlocked on key questions about how to proceed.

"Some members of the Working Group provided reasons as to why policy development to address fast flux is outside the scope of ICANN's remit, while others disagreed," the interim report (PDF) stated. "Gaining a common appreciation and broad understanding of the motivations behind the employment of fast flux or adaptive networking techniques proved to be a particularly thorny problem for the WG."

By now, most people who follow current security events know that fast-flux hosting is a way to bring resiliency to botnets used in criminal spam and phishing operations. By using peer-to-peer technology to rapidly change the location of the rogue network's master control channel, there is no single point of weakness for security response teams to bring down. Some of the world's biggest botnets, including Waledac, Asprox and the now-defunct Storm have used it to thrive, despite considerable efforts by white hats to stop them.

"When used by criminals, the main goal of fast-flux hosting is to prolong the period of time during which the attack continues to be effective," according to the report, which was six months in the making. "It is not an attack itself - it is a way for an attacker to avoid detection and frustrate the response to the attack."

But some members of the working group say fast flux has more beneficial applications. Content distribution networks such as Akamai use it to add and drop servers on the fly, perform load balancing, and reduce latency, for example. The report also cited a free-speech group called UltraReach, which claims to use fast flux to circumvent internet censorship by the Chinese government.

"Some solutions aimed at criminal activity could prohibit or constrain non-criminal activity that use similar techniques, or might not differentiate adequately based on the intent of the activity," the report warned. "Whether solutions to criminal fast-flux may constrain non-criminal services and/or the creation of new and legitimate services on the Internet are pertinent issues for consideration."

The report lays out a variety of approaches ICANN can take to limit the use of fast-flux hosts by criminal organizations. One approach involves the gathering and sharing of additional information about registered domains so that it's easier to identify those used in criminal fast-flux operations.

Others call for restrictions on the use of certain types of so-called TTLs, or times to live, which control how long the IP address of a given domain name is cached on a domain-name system server. Fast flux typically uses extremely short TTLs in an effort to constantly scramble the location of a botnet's control channels.

But all of that is purely hypothetical right now, as the 121-page report, prepared at the behest of ICANN's Generic Names Supporting Organization, makes clear. For now, the working group is still struggling to define precisely what fast flux is and whether it's something the group should assert control over. And for that, it's hoping to hear from you. ®

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