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IP flooding by using broadcast address
by Edward Henigin 20 Jul '97

20 Jul '97

We're seeing a pernicious sort of DOS attack lately. The attack takes advantage of hosts IP stack implementation, and how it deals with ICMP packets to the broadcast address. Basically, the short and sweet of it is that most hosts will respond to an echo-request to its broadcast address with an echo reply. So imagine this scenario: some disgruntled hax0r forges his source address to be your web server (or shell server, or irc server, or whatever) and sends some broadcast pings to a well populated remote network. His/her ping will be amplified by the number of hosts on the remote network. Here is an example to illustrate: In one window, I did this: (ed) spanky:~$ ping 205.236.175.255 205.236.175.255 is alive (ed) spanky:~$ In another, this: (root) spanky:~# snoop -d isptp0 proto icmp Using device /dev/isptp (promiscuous mode) spanky -> 205.236.175.255 ICMP Echo request toolbox.total.net -> spanky ICMP Echo reply falcon.total.net -> spanky ICMP Echo reply annex-08.mtl.total.net -> spanky ICMP Echo reply 199.166.230.99 -> spanky ICMP Echo reply gig.net -> spanky ICMP Echo reply 205.236.53.122 -> spanky ICMP Echo reply middletown.total.net -> spanky ICMP Echo reply 205.236.53.199 -> spanky ICMP Echo reply server95.total.net -> spanky ICMP Echo reply 205.236.175.20 -> spanky ICMP Echo reply freddy.total.net -> spanky ICMP Echo reply 205.205.162.10 -> spanky ICMP Echo reply tors.accent.net -> spanky ICMP Echo reply lightning.total.net -> spanky ICMP Echo reply c4700-01.mtl.total.net -> spanky ICMP Echo reply as5200-35.mtl.total.net -> spanky ICMP Echo reply newsfeeder.total.net -> spanky ICMP Echo reply annex-03.mtl.total.net -> spanky ICMP Echo reply annex-02.mtl.total.net -> spanky ICMP Echo reply as5200-31.mtl.total.net -> spanky ICMP Echo reply as5200-30.mtl.total.net -> spanky ICMP Echo reply phoenix.total.net -> spanky ICMP Echo reply bretweir.total.net -> spanky ICMP Echo reply 205.236.175.10 -> spanky ICMP Echo reply wacky.total.net -> spanky ICMP Echo reply 205.236.87.200 -> spanky ICMP Echo reply annex-01.mtl.total.net -> spanky ICMP Echo reply annex-10.mtl.total.net -> spanky ICMP Echo reply as5200-06.mtl.total.net -> spanky ICMP Echo reply as5200-33.mtl.total.net -> spanky ICMP Echo reply as5200-13.mtl.total.net -> spanky ICMP Echo reply as5200-34.mtl.total.net -> spanky ICMP Echo reply annex-09.mtl.total.net -> spanky ICMP Echo reply as5200-28.mtl.total.net -> spanky ICMP Echo reply annex-06.mtl.total.net -> spanky ICMP Echo reply as5200-08.mtl.total.net -> spanky ICMP Echo reply as5200-22.mtl.total.net -> spanky ICMP Echo reply as5200-36.mtl.total.net -> spanky ICMP Echo reply as5200-03.mtl.total.net -> spanky ICMP Echo reply cradlerock.total.net -> spanky ICMP Echo reply as5200-26.mtl.total.net -> spanky ICMP Echo reply as5200-37.mtl.total.net -> spanky ICMP Echo reply c4700-02.mtl.total.net -> spanky ICMP Echo reply www.greernet.com -> spanky ICMP Echo reply 199.166.230.69 -> spanky ICMP Echo reply ns2.accent.net -> spanky ICMP Echo reply rizzo.infobahnos.com -> spanky ICMP Echo reply www.webquebec.com -> spanky ICMP Echo reply annex-07.mtl.total.net -> spanky ICMP Echo reply as5200-12.mtl.total.net -> spanky ICMP Echo reply as5200-32.mtl.total.net -> spanky ICMP Echo reply as5200-19.mtl.total.net -> spanky ICMP Echo reply as5200-02.mtl.total.net -> spanky ICMP Echo reply as5200-29.mtl.total.net -> spanky ICMP Echo reply as5200-11.mtl.total.net -> spanky ICMP Echo reply as5200-20.mtl.total.net -> spanky ICMP Echo reply as5200-10.mtl.total.net -> spanky ICMP Echo reply as5200-21.mtl.total.net -> spanky ICMP Echo reply as5200-16.mtl.total.net -> spanky ICMP Echo reply as5200-15.mtl.total.net -> spanky ICMP Echo reply as5200-05.mtl.total.net -> spanky ICMP Echo reply as5200-01.mtl.total.net -> spanky ICMP Echo reply irc.total.net -> spanky ICMP Echo reply as5200-25.mtl.total.net -> spanky ICMP Echo reply as5200-04.mtl.total.net -> spanky ICMP Echo reply squid.total.net -> spanky ICMP Echo reply 205.236.175.12 -> spanky ICMP Echo reply as5200-14.mtl.total.net -> spanky ICMP Echo reply pico.total.net -> spanky ICMP Echo reply c4700-03.mtl.total.net -> spanky ICMP Echo reply nic2.total.net -> spanky ICMP Echo reply under.total.net -> spanky ICMP Echo reply annex-04.mtl.total.net -> spanky ICMP Echo reply 198.168.57.42 -> spanky ICMP Echo reply as5200-09.mtl.total.net -> spanky ICMP Echo reply as5200-24.mtl.total.net -> spanky ICMP Echo reply as5200-27.mtl.total.net -> spanky ICMP Echo reply as5200-23.mtl.total.net -> spanky ICMP Echo reply as5200-17.mtl.total.net -> spanky ICMP Echo reply as5200-18.mtl.total.net -> spanky ICMP Echo reply as5200-07.mtl.total.net -> spanky ICMP Echo reply (I've already been in contact with Total Access Inc, and they were most cooperative in putting filters on their networks to prevent this from happening again.) In the above example, you see that a single echo request resulted in 81 echo replies, an 81x amplification of Internet traffic. A 28.8Kbps Internet connection becomes 2332.8Kbps, about a T1 and a half, worth of bandwidth, when amplified 81 times. You well know that this much traffic is more than enough to peg a small ISP. If one of these fiends either a) enlists the help of a few friends, all on 28.8 connections, or b) does this sort of thing from an open box on a higher speed university connection, well, they can take down even larger ISP's. What you need to do is put filters on your routers to prevent broadcast packets from entering your network. I believe that some networks, like Total Access Inc's, are among a list of "known" networks that can be used as part of a "portfolio", if you will, of networks that can be used to attack other networks. Everyone needs to be doing the following: 1) Keep measured traffic stats, and look at them, using something like MRTG. 2) Filter all broadcast traffic from coming into your network. I believe that it's QUITE rare to have an application that is both *routed* and uses the broadcast address. This is made harder when you VLSM, but I belive the majority of networks are provisioned on an 8 bit boundary, so you can filter 90% of the traffic by filtering to the .255 address. 3) Re-iterating what people have said before, filter outbound traffic to allow only *your* host traffic from getting out. This makes you a responsible Internet citizen, by preventing people from using your network to launch attacks such as this against others. I think it would be very wise of cisco to have a global flag (or at least, a per-interface flag) which would prevent the forwarding of a packet to an all-ones address. If cisco won't add this feature, maybe Ascend will in their GRF, and maybe a few more GRF's will be sold because of it. Thank you for your time. Edward Henigin Engineering Director, Texas Networking, Inc. ed(a)texas.net (512) 427-1655 Alternate POC's for Texas.Net: Michael Douglass Senior Systems Engineer mikedoug(a)texas.net Bill Bradford Systems Administrator mrbill(a)texas.net Jonah Yokubaitis President barron(a)texas.net

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Quote of the day!
by jamie＠comet.net 20 Jul '97

20 Jul '97

From someone-I-can't-name-cuzza-their-job: "MFS is the spawn of satan, it's all a conspiracy to send us back to the dark ages of hand-written communication." jamie jamie(a)comet.net *************************************************************************** For PGP public key, mail me with Subject:GET KEY For random Ambrose Bierce quote, Mail me with Subject: ambrose Support the anti-Spam amendment - Join at http://www.cauce.org/ "Microsoft was invented by domestic terrorists. Remember, it's no longer an import industry."

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default routes on Ciscos
by Nick Lauriat 19 Jul '97

19 Jul '97

Hi there! Just curious if anyone out there knows of a way to configure default routes on a per interface basis on a Cisco. So that different interfaces had different default routes statically defined. Any thoughts? Thanks! Nick Lauriat

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Re: silly tiers; treno
by Barb Dijker 19 Jul '97

19 Jul '97

A sales rep doesn't need the concept of tiers to spread misinformation and have delusions of granduer. Here's a question I got from a potential customer wanting a backup link from us but needing to de-program his boss. >My bosses' major concern is that UUNet claims Sprint as one of their >customers, and he wants proof that the COOP's Sprint connection is not >traveling on the UUNet backbone. I know that we have a dedicated link to >Cheyenne, but what happens after there? Barbara L. Dijker, Executive Director =============================================== Colorado Internet Cooperative Association 2525 Arapahoe Ave E4-280, Boulder CO 80302-6724 Voice: +1 303 443 3786, FAX: +1 303 443 5162 WWW: http://www.coop.net/

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Re: DC fiber cut: field report
by Joe McGuckin 19 Jul '97

19 Jul '97

I thought the nitrogen pressurisation was to keep the copper cables dry...

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Re: tiers? (fwd)
by Danny 19 Jul '97

19 Jul '97

Does everyone agree with this, it's the only response I have received thus far (and according to the list, the sender works for a tier 1 provider). [snip] Tier 1: _Owns the fiber_, Multiple coast to coast paths of significant bandwidth Tier 2: Reseller, Major connections (DS3/OC3) to multiple tier 1 providers. Possibly: Major connections to one (1) tier 1 provider. Tier 3: Everybody else. > > Anyone care to take a stab at what places a provider in > a given "tier-group"? Seems to me as though the large(st) > providers are a bit harsher (naturally) than the smaller > providers.

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tiers. A measurement tool.
by Mark Kent 18 Jul '97

18 Jul '97

Clearly the definition of tiers varies over time. I think that the tools needed to "measure" the current tier-ness of providers are: a) a full bgp table (not just a full route table... if net FOO appears behind AS3561, AS1239 and AS1 then you want all three entries). b) a suitably large group of companies whose net access depends on how you extract a route table from the full bgp table c) a stopwatch d) a phone The procedure is basically to eliminate an AS from getting in the route table and timing how fast the phone rings. Then you just need a scale, something like this 0 - 2 minutes: Tier 1 2 - 10 minutes: Tier 2 etc. In some cases you can replace the stopwatch with a calendar. You can flesh out this methodology with extras like frequency of calls, duration of calls, language used in the calls, whether you are threatened or not, whether your family is threatened, etc. This technique has been used by some service providers by way of their peering strategy. -mark

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RE: DC fiber cut: field report
by Steve Martin 18 Jul '97

18 Jul '97

Correct you are! Having spent 7 years of my career doing large OSP (OSP in this case is Outside Plant) installations around the country including direct buried, ducted and aerial I can confirm that these techniques are routinely employed. That makes 2 cable weenies! -S -----Original Message----- From: Jay R. Ashworth [SMTP:jra@scfn.thpl.lib.fl.us] Sent: Friday, July 18, 1997 2:38 PM To: Owen DeLong Cc: Dave O'Shea; stephen(a)clark.net; nanog(a)merit.edu Subject: Re: DC fiber cut: field report On Fri, Jul 18, 1997 at 11:59:11AM -0700, Owen DeLong wrote: > Gee, makes a good case for putting innerduct inside conduit and putting > gas through it just to discourage BIFF. :-) Am I the only one who's a cables and switches weenie enough to know that the telco's _already do this_? Large numbers of local multi-pair trunking cables are pressurized with nitrogen, and they put pressure drop alarms on them, so they know if one takes a hit. Cheers, -- jra -- Jay R. Ashworth jra@bayli nk.com Member of the Technical Staff Unsolicited Commercial Emailers Sued The Suncoast Freenet "People propose, science studies, technology Tampa Bay, Florida conforms." -- Dr. Don Norman +1 813 790 7592

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BHTC
by Michael Kindig - Compute Intensive 18 Jul '97

18 Jul '97

BHTC - Back-Hoe Technology Certification There may be a need for all back-hoe aoperators to obtain a telco certification. Perhaps, these back-hoe unions could then sub-contract through telco agencies...picture this! "Hello, AT&T back-hoe. How can I help you?" or "Worry no-mo with UUnet Back-Hoe!" Michael Kindig - NETWORK INTENSIVE CUSTOMER ENGINEERING DEPT ____________________________________________________________ 8001 Irvine Center Dr 1130 __o URL :http://www.ni.net Irvine, CA 92618-2933 _ \<_ Phone:714.450.8400 mkindig(a)compute.com (_)/(_) Fax :714.450.8410

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Outages in the News
by Dan Dale 18 Jul '97

18 Jul '97

http://www.mmp.co.uk/mmp/informer/netnews/HTM/718n1k.htm Are all our jobs in jeopardy? Dan

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