North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: TCP/BGP vulnerability - easier than you think

  • From: Iljitsch van Beijnum
  • Date: Wed Apr 21 09:11:21 2004 
On 21-apr-04, at 14:38, Daniel Roesen wrote:


So the attacker sends a spoofed SYN to router A, and router A sends an
RST to router B and router B terminates the BGP session.



Correct.





The good part here is that filtering RSTs should still work.





It doesn't. The RST are then being sent by the authorized sender and

your edge anti-spoof filtering for RST doesn't help a single
millimeter.



Now it's your time to overlook something: the filters I listed in my
earlier message simply filter RSTs to/from the BGP port without looking
at the address fields. Filtering ALL RSTs is probably a bad idea as
broken sessions will then have to time out, possibly inconveniencing
users (and thereby generating support calls). But for BGP this isn't
much of an issue as the BGP hold timer takes care of business here
anyway. So I believe filtering out all BGP RSTs on all edges is
probably a good idea.