DNS rebinding attacks are real and can be carried out in the real world. They can penetrate through browsers, Java, Flash, Adobe and can have serious implications for Web 2.0-type applications that pack more code and action onto the client. Such an attack can convert browsers into open network proxies and get around firewalls to access internal documents and services. It requires less than $100 to temporarily hijack 100,000 IP addresses for sending spam and defrauding pay-per-click advertisers. Everyone is at risk and relying on network firewalls is simply not enough.
In a paper released by Stanford Security Lab, "Protecting Browsers from DNS Rebinding Attacks," authors Collin Jackson, Adam Barth, Andrew Bortz, Weidong Shao, and Dan Boneh provide ample detail about the nature of this attack as well as strong defenses that can be put in place in order to help protect modern browsers.
In the following section from the paper, the authors explain how DNS Rebinding Attacks are implemented and why a well-known existing defense against these attacks, called "DNS pinning," is simply ineffective in modern browsers.
Introduction to DNS Rebinding Attacks
To mount this attack, the attacker did not compromise any DNS servers. The attacker simply provided valid, authoritative responses for attacker.com, a domain owned by the attacker. This is very different from "pharming" attacks where the attacker must compromise a host name owned by the target by subverting a user's DNS cache or server.
Pinning is no longer an effective defense against DNS rebinding attacks because current browsers use plug-ins to add functionality to web pages. The browser and each plug-in maintain separate pin databases, creating a new class of vulnerabilities we call multi-pin vulnerabilities that permit an attacker to mount DNS rebinding attacks. We demonstrate, for example, how to exploit the interaction between the browser and Java LiveConnect to pin the browser to one IP address while pinning Java to another IP address, permitting the attacker to read and write data directly on sockets to a host and port of the attacker's choice despite strong pinning by each component. Some of these attacks have been discussed recently in the black-hat community.
Our experiments show how an attacker can exploit multi-pin vulnerabilities to cheaply and efficiently assemble a temporary, large-scale bot network. Our findings suggest that nearly 90% of web browsers are vulnerable to rebinding attacks that only require a few hundreds of milliseconds to conduct. These attacks do not require users to click on any malicious links: users need only view an attacker's web advertisement. By spending less than $100 on advertising, an attacker can hijack 100,000 unique IP address to send spam, commit click fraud, or otherwise misuse as open network proxies.
The above introduction to DNS Rebinding Attacks is reproduced here with permission from the Stanford Security Lab and the authors of the paper, "Protecting Browsers from DNS Rebinding Attacks". Links provided within the article are included by CircleID for your reference.
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