Whitepaper - DNS pinning and web proxies
DNS-based attacks against browsers have been known about for years. These
attacks have received increased attention recently, following the discovery
of defects within browser-based DNS pinning defences.
So far, discussion has focused on browser issues. However, the same attacks
can also be performed against web proxies. Browser-based DNS pinning does
not apply when a web proxy is being used, because the DNS look-ups occur on
the proxy, not the browser. Hence, even if DNS-based attacks are completely
addressed within browsers, the problem is not going to go away altogether.
The most significant opportunities for DNS-based attacks are against web
users on internal corporate networks, as a means of gaining unauthorised
access to sensitive information and web applications on internal intranets.
Given that a large proportion of these users access the Internet via a proxy
server, attacks against web proxies may represent at least as significant a
threat as those against browsers.
I've written a short paper which explains the problem, examines possible
software-based solutions, and describes the defences that organisations and
individuals can use to prevent attacks against them. You can find the paper
here:
http://www.ngssoftware.com/research/papers/DnsPinningAndWebProxies.pdf
Cheers,
Dafydd Stuttard
Principal Security Consultant
NGS Software Ltd
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