Subject: [Sip] DoS mitigation feature: Via route block

From: "Jeroen van Bemmel" <[email-masked]>
Date: Fri, 16 Sep 2005 00:35:03 +0200

Consider the following feature: A UA may ask its home proxy to block any requests coming via a particular set of intermediaries. So if the UA finds itself under attack and receives requests with Vias V1, V2, V3, V4 (V4 being the one presumably inserted by the attacker), it could say "please drop all messages coming via [ V1, V2, V3 ]". The V's could e.g. only be based on the sent-by portion of each Via.

Such a "Via route block" would be associated with the current registration, and expire when it does.

This would of course only work in cases where an attacker has little control over the intermediaries. Moreover, things like spiralling attacks (using explicit routing) would have to be considered.

Any thoughts?

Regards,

Jeroen

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