North American Network Operators Group

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Re: Consumers of Broadband Providers (ISP) may be open to hijack attacks (fwd)

  • From: Valdis . Kletnieks
  • Date: Wed Jul 19 14:08:19 2006

On Wed, 19 Jul 2006 02:02:20 CDT, Gadi Evron said:

> 	Some ISP networks do not reset open TCP connections of customers that
> were either cut-off by the ISP or cut off by self-initiation.  While it is 
> responsibility of every person to terminate every open connection before
> link termination, when the ISP initiates this, it cannot be guaranteed.  A 
> customer who happens to resume a recycled dynamic IP can then read the 
> previous persons open sessions.

Low threat level indeed.  The following *ALL* need to happen for it to be a

1) You need to get disconnected unexpectedly.
2) Your IP address needs to be re-assigned quickly - before the ISP's routing
hardware has a chance to send too many ICMP Dest Unreachable and cause a
connection shutdown.
3) Your IP address needs to be handed to a malicious user.
4) Said malicious user has to be running an IP stack configured to *NOT*
send back a TCP RST or ICMP Port Unreachable when a packet comes in.
5) The connection being hijacked needs to have in-flight data that will be
retransmitted or a keep-alive packet or other similar hint to the attacker
that the connection exists.

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