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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: attacking DDOS using BGP communities?
701 has a blackhole community, 701:9999, basically it sets the next-hop to something blackholed on their edge so the DOS attack gets dropped as soon as it hits them. I have made use of this to kill at least one DDOS event. A global blackhole community may be difficult to achieve, but getting the majority of large providers to implement one is a good start. -----Original Message----- From: Saku Ytti [mailto:[email protected]] Sent: Thursday, October 17, 2002 5:23 PM To: [email protected] Subject: attacking DDOS using BGP communities? How feasible would these ideas be? 1) Signaling unwanted traffic. You would set community which would just inform that you are receiving unwanted traffic. This way responsible AS# with statistical netflow could easily automaticly search for these networks and report to NOC if both there is increased traffic to them and community is on. -would it be affective at all? Could your netflow parser use it easily? +wouldn't need big changes 2) 'TTL' community. You would have ~10 communities representing how many AS hops until route should not be advertised anymore. If you would experience DOS you'd start from TTL 1 and increase until DOS flow starts again, with any luck you would end up having very limited amount of AS# to communicate with in hopes of fixing their anti-spoofing filters and to catch malicious party. -just think about the amount of route-maps :> -you would need to flap the network possible 10 times == damped +some idea who to contact w/o co-operation of NOCs (can be hard) +wins you time, often DOS is over before you've reached 3rd AS number to ask where the traffic is originating. 3) 'null route' community. This would only be useful if it would mean that you are also accepting more spesific annoucement, preferally even /32. Most people are propably crying about the idea already, but if you plan it wisely with prefix-limit setting it might not be suicide. Just remember that all downstream prefix-limit+your prefices must be smaller than what your upstream has set for prefix-limit, if this is not done then your downstreams can effectively trigger your upstream prefix-limit killing your connectivity. How AS handles the 'null route' community could vary, others set next-hop to null0 other might set it to analyzer tool. Just that it shouldn't reach the other end anymore. -the obvious: explosion of global bgp routing table (no, not nececcarily) +effective, you'd instantly free your link from any DOS traffic to given destination. -- ++ytti
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