Feeds

Fast flux foils botnet takedown

Many-headed foe hard to combat

The Essential Guide to IT Transformation

During one investigation for the Okie Island Trading Company in May, Shaw ran into a fast-flux bot net linked to a phishing site that mimicked a North Carolina bank.

A simple lookup on the phishing site's domain name - from China's address space - immediately turned up five different IP addresses. Rather than deal with shutting down a single server, Shaw now had to deal with five different computers, each likely owned by an unwitting end user infected with bot software. Yet, the attacker didn't stop at five: When Shaw rechecked the domain name six minutes later, three of the addresses had changed. Eventually, tens, or even hundreds, of Internet addresses would rotate through the name server.

"It's like a hydra, with all these heads," Shaw said. "The only way to kill it is to convince the registrar to shut down the domain."

Yet, registrars and Internet service providers are rarely eager to go after bot-infected customers. Shutting down an Internet address or a domain name could mean angering a legitimate customer and would likely lead to expensive support calls. It's no wonder that ISPs and registrars are hesitant to take down potentially infected machines, said Adam Waters, chief operating officer for Support Intelligence, which provides customers security monitoring services.

"When you call them up, you are asking them to take their customers offline," Waters said in a recent interview. "Any business that you ask to do that, well, they are going to be gun shy."

Earlier this year, Support Intelligence found a number of zombie computers that appeared to be located inside the networks of major corporations. When the company tried to contact the corporations involved, few returned the calls. So the security-monitoring firm started highlighting several companies on its blog - a move that brought quicker responses.

Getting registrars to take down domain names is even more difficult, however. And even if successful, repeating that success often enough to fully take down a bot net with distributed DNS is almost impossible, Waters said.

"Fast flux is not about the bad guys hiding where they are," he said. "They are in your face and saying, 'Come take us out.' And you can't."

Top-level domain name registrars - the arbiters of .com, .net, .org and the country-specific domains - could solve the problem by refusing to allow fast-changing domains or by making the takedown process for domains easier. However, making the use of such power routine would worry many people, said Gadi Evron, a bot-net expert and security evangelist for Beyond Security.

"Even if you enable some sort of control at the top-level domain, (you have to ask) do we really want to give them the authority to do that?" Evron said in a recent interview. "I'm all for it, because we have no controls in place to mitigate what is being abused, not to mention, prevent it all together."

Until takedown through the registrars become easier, defenders will have to resign themselves to increasingly difficult-to-disable bot nets, said Johannes Ullrich, chief technology officer for the SANS Internet Storm Center. In the past, only a third of bot nets lasted more than 24 hours. By design, fast-flux bot nets last much longer and, just by their ability to outlive IRC-based bot nets, will likely soon make up the majority of attack networks on the Internet.

"There may not be all that many more conversions to fast-flux DNS, but once we see a bot net converted to fast flux, it's likely that the bot net will be around for a long while," Ullrich said.

With the prospect of having to track down each infected PC, rather than a single key computer, security experts concerned about Internet safety should focus on stopping the initial spread of bot software, he added.

"You have to prevent it, because once you are infected, it's game over," Ullrich said.

This article originally appeared in Security Focus.

Copyright © 2007, SecurityFocus

Build a business case: developing custom apps

More from The Register

next story
14 antivirus apps found to have security problems
Vendors just don't care, says researcher, after finding basic boo-boos in security software
Only '3% of web servers in top corps' fully fixed after Heartbleed snafu
Just slapping a patched OpenSSL on a machine ain't going to cut it, we're told
How long is too long to wait for a security fix?
Synology finally patches OpenSSL bugs in Trevor's NAS
Israel's Iron Dome missile tech stolen by Chinese hackers
Corporate raiders Comment Crew fingered for attacks
Roll out the welcome mat to hackers and crackers
Security chap pens guide to bug bounty programs that won't fail like Yahoo!'s
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
Researcher sat on critical IE bugs for THREE YEARS
VUPEN waited for Pwn2Own cash while IE's sandbox leaked
Four fake Google haxbots hit YOUR WEBSITE every day
Goog the perfect ruse to slip into SEO orfice
Secure microkernel that uses maths to be 'bug free' goes open source
Hacker-repelling, drone-protecting code will soon be yours to tweak as you see fit
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.