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Flaw Leaves Internet Open to Attacks

malebolgia   on 20 April 2004 - 20:29 · 7 comments & 925 views

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A security researcher has developed a new attack for a well-known flaw in the TCP protocol that allows an attacker to effectively shut down targeted routers and terminate existing TCP sessions at will. The scenario has many security experts worried, given the ubiquity of TCP and the fact that there's an attack tool already circulating on the Interne

The basic problem lies in the fact that existing TCP sessions can be reset by sending specially crafted RST (reset) or Syn (synchronization) packets to either of the machines involved in the session. This is in fact an intended feature of the protocol. However, the source IP addresses on these packets can be forged, which makes it possible for attackers not involved in the TCP session to terminate the connection, causing a de facto denial of service.

News source: eWeek


apparently already posted (last october) - email sent to those prats @ bastion...

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#1 Ben on 20 Apr 2004 - 20:43
Crumbs! Is this as serious as it sounds. It makes sense in my head, but I wonder why no one has ever thought of it before?
(1 reply) #2 shaark on 20 Apr 2004 - 21:08
it'll be so easy to kill bittorrent leechers. Just open a torrent, scan the leechers connected to the torrent and reset their session.
#2.1 Huezo on 21 Apr 2004 - 01:26
Dont give them ideas!

(1 reply) #3 me101 on 20 Apr 2004 - 21:09
From what's i've read, this is a big concerns for BGP routing tables, who's peer connections can be open for long periods of time. Managing to close these long opened connections can cause these routers to "flap" and thus routes disappear, meaning that parts of the net "could" become unreachable...

From the mailing lists I've seen, it's already being handled by the major ISP's, who are making their BGP connections hardened with md5 checksums between peers etc... It's all in hand by the big boys
#3.1 Jon on 21 Apr 2004 - 08:02
That sounds like good info.
#4 darthfader on 20 Apr 2004 - 21:11
time to start using something like BIC-TCP
#5 Wrath Delivery on 21 Apr 2004 - 07:05
It is difficult for most individuals connected to the net to forge source addresses in their packets because the ISP will in most case perform packet inspection on all traffic routed to and from their clients. In fact a buddy of mine once tried it and his connection immediatly dropped and he was called a minute later by the ISP and warned not to do that again. To spoof these days you need to be an ISP or backbone provider employee or you need to hack into such a network first.

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