A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the TCP Maintenance and Minor Extensions Working
Group of the IETF.
Title : Improving TCP's Robustness to Blind In-Window Attacks
Author(s) : R. Stewart, M. Dalal
Filename : draft-ietf-tcpm-tcpsecure-05.txt
Pages : 25
Date : 2006-6-16
A recent study indicates that some types of TCP connections have an
increased vulnerability to spoofed packet injection attacks than
previously believed [SITW]. TCP has historically been considered
protected against spoofed packet injection attacks by relying on the
fact that it is difficult to guess the 4-tuple (the source and
destination IP addresses and the source and destination ports) in
combination with the 32 bit sequence number(s). A combination of
increasing window sizes and applications using a longer term
connections (e.g. H-323 or Border Gateway Protocol [RFC1771]) have
left modern TCP implementation more vulnerable to these types of
spoofed packet injection attacks.
Note: Both [SITW] and [I-D.touch-tcp-antispoof] provide charts which
can give the reader an idea as to the time it takes to penetrate an
Many of these long term TCP applications tend to have predictable IP
addresses and ports which makes it far easier for the 4-tuple to be
guessed. Having guessed the 4-tuple correctly, an attacker can
inject a RST, SYN or DATA segment into a TCP connection by carefully
crafting the sequence number of the spoofed segment to be in the
current receive window. This can cause the connection to either
abort or possibly cause data corruption. This document requires
small modifications to the way TCP handles inbound segments that can
reduce the probability of such an attack.
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