CAPTCHA fun

Thursday, March 13. 2008
Websense had a few weeks ago a story on "Google’s CAPTCHA busted in recent spammer tactics". The basic idea is that the attacker automatically signs up for freemail accounts (e.g., Google or live.com) with the help of certain malware. During the registration process, the attacker needs to solve a CAPTCHA. This can be done for example with the help of humans which are paid for this task. Another option is to use humans who want to access a certain service, e.g., a porn website. This is the cheaper option, and presumably also effective. An example of such a CAPTCHA attack is currently available at gift-vip.net. Caution: this is not work-safe and do not open it if you do not want to see adult content. I also created a short movie which illustrates this process. The movie is also available as .mov and .swf file.

Thanks a lot Nick FitzGerald for this tip!

[Update]: Please be careful when opening the actual site since it also contains a malicious iframe.
Posted by Thorsten Holz in malware at 12:16 | Comments (0) | Trackbacks (0)

SSAC Advisory on Fast Flux Hosting and DNS

Thursday, March 13. 2008
The Security and Stability Advisory Committee (SSAC) of ICANN released an advisory regarding "Fast Flux Hosting and DNS", in which they detail ICANN's view of FFSNs. Thanks Jose for the heads-up!

Introduction

"Fast flux" is an evasion technique that cyber-criminals and Internet miscreants use to evade identification and to frustrate law enforcement and anticrime efforts aimed at locating and shutting down web sites used for illegal purposes. Fast flux hosting is an application of technology that supports a wide variety of cyber-crime activities (fraud, identity theft, online scams) and is considered one of the most serious threats to online activities today. Basic fast flux hosting uses rapid modification of IP addresses associated with a system that hosts a malicious activity to evade detection and take down efforts. This technique is also used to rapidly modify the IP addresses of the name servers that resolve the domain names of the fluxed malicious hosts (this variant is sometimes called NS fast flux). A particularly troublesome variant of fast flux hosting, "double flux", fluxes addresses of both name servers and malicious (web server) hosts.

This Advisory describes the technical aspects of fast flux hosting and fast flux service networks. It explains how the DNS is exploited to abet criminal activities that employ fast flux hosting, identifying the impacts of fast flux hosting, and calling particular attention to the way such attacks extend the malicious or profitable lifetime of the illegal activities conducted using these fast flux techniques. It describes current and possible methods of mitigating fast flux hosting at various points in the Internet. The Advisory discusses the pros and cons of these mitigation methods, identifies those methods that SSAC considers practical and sensible, and recommends that appropriate bodies consider policies that would make the practical mitigation methods universally available to registrants, ISPs, registrars and registries (where applicable for each).
Posted by Thorsten Holz in paper at 08:31 | Comment (1) | Trackbacks (0)
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