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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Proactive steps to prevent DDOS?
So which one of those things do you think any of the victims wasn't
doing before, and how will the steps now prevent a future DDOS
attack from affecting its servers? If the victims had done all of
these things before they were attacked, would it have prevented the
attack from affecting their service?
Those aren't just rhetorical questions, I'm trying to understand
how to approach this.
If you view DDOS as a traffic surge, can we use any lessons from
other phenomenon involving surges, such as vehicle traffic at rush
hour, water runoff from a storm, lightning strike.
You can't control the weather, but you can do a lot to mitigate
the damages.
Methods for handling surges:
- Limit the source (e.g. metering lights on freeways)
- Divert the surge (e.g. lightning arresters on electric circuits)
- Buffer the surge (e.g. detention basins for water runoff)
How can we signal uncooperative sources to limit or even cease sending
traffic? Preferablly without impacting cooperative sources. Historically,
the "nice guys" traffic gets throttled, while the "bad guys" traffic
blasts through. If you don't get enough tokens or credits, you don't
send. RED and friends work with cooperative sources.
How can we identify and drop the excess traffic at the earliest point?
Should it be a cascaded system, i.e. you have several stages instead
of one big muttha firewall. Do you really want to carry the traffic
across the entire Internet, just to drop it on the last link?
How can we size the protective systems and the final system so we won't
overrun their available resources (requires knowing how large the
resources actually are)?
Is there anyway to mitigate the slashdot effect for small sites as well
as large sites? Larges sites can throw more capacity at the problem
to buffer the surge.
Its been at least a week since someone suggested putting a bad idea
into DNS. How about using the inability to reach the DNS server to
rate limit the sources. Every once in a while, the IP stack (protocol
layer violation) queries the in-addr.arpa servers for the destination
network. The in-addr.arpa servers respond with additional credits,
or zero credits (source quench), or don't respond signalling the
source to switch to a conservative transmission mode. If you don't
trust the end-to-end system to respond to the signals, the upstream
edge router could enforce it.
Is that idea horrendous enough?
On Sat, 27 January 2001, Jeff Ogden wrote:
> >At 4:15 PM -0800 1/26/01, Sean Donelan wrote:
> >Fine, does this work better for you?
> >
> >Help me, what proactive steps can I take to protect my network from a DDOS?
>
> There isn't a lot that can be done, but there are a few steps you can
> take to "get ready" for a DDOS attack.
>
> --Make sure you have monitoring of your routers or firewalls in place
> so you'll get an early alert of a possible DOS attack. This will at
> least allow you to start working on the problem (and drafting
> press releases :-).
>
> --Talk to all of your up stream providers so you know how to contact and
> work with them if they are a source of a DOS attack against you. If your
> up stream provider isn't willing to work with you on this, start the
> process of getting a new up stream provider.
>
> --Look into the systems that are being developed and starting to become
> available that help automate the work to diagnose DDOS attacks.
> Encourage your up streams to do the same.
>
> --Make sure you have in place the filtering on your own networks that you
> wish everyone else had in place on their networks. This won't protect
> you from being attacked, but it will prevent you and your users from
> attacking others (or at least using spoofed IP addresses to do so), and
> that in turn may prevent you from being the target of a retaliatory DOS
> attack. It can also prevent or limit the spread of a DOS attack that
> originates within your network or from someone down stream. From your
> customer's point of view there may not be much difference between
> you being the source of or the target of a DOS attack--either way
> performance is likely to be poor and customers are likely to be unhappy.
>
> -Jeff Ogden
> Merit
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