From: Leigh Harrison (ccileigh@gmail.com)
Date: Thu Aug 24 2006 - 13:40:45 ART
All,
To throw my hat(white ;-) into the ring - have a look at some of these
links:-
Definitions of a Smurf and Fraggle attack:-
http://en.wikipedia.org/wiki/Fraggle_attack
http://en.wikipedia.org/wiki/Smurf_attack
http://www.unixcities.com/dos-attack/index1.html
http://www.networkdictionary.com/security/SmurfAttack.php
http://www.javvin.com/networksecurity/SmurfAttack.html
And for those of you that don't believe the links, here is the c code
for a smurf and fraggle attack, so that you can build you defences on
your labs and fire the attacks at them. Then you'll really have a
definitive answer. There's one for an icmp flooding attack too.
http://www.phreak.org/archives/exploits/denial/fraggle.c
http://www.phreak.org/archives/exploits/denial/smurf.c
http://www.phreak.org/archives/exploits/denial/icmplog.c
Enjoy
LH
PS - I found all of these links with a quick search on google - I don't
have a private stash of DoS scripts!!
Scott Morris wrote:
> And so.... In the great spirit of learning, should you not come up with a
> proposed solution as well? That way we can all benefit from the thinking
> through of things!!!
>
> While I do appreciate being singled out for opinions, and I'm sure Brian
> Dennis and Brian McGahan do as well, bear in mind that the answers to any
> given question don't necessarily count as the only ones, not should they be
> looked at as something to memorize and treat as THE right answer.
>
> When learning any topic, the discussion and the thinking through things is
> often where the best learning comes from.
>
> So what things do you have there... You aren't trying to kill the traffic
> according to your scenario, you're simply trying to log it. So what are the
> pieces (there will only be permits I'm guessing) involved? And is logging
> already setup? :)
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
> #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPExpert VP - Curriculum Development
> IPExpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> David Redfern (AU)
> Sent: Thursday, August 24, 2006 5:40 AM
> To: ccielab@groupstudy.com
> Subject: RE: ICMP Flooding vs SMURF Attack---THE BRIANS AND SCOTT
>
> Guys,
>
> As i think we can all agree that the answer may vary depending on the
> question and requirements, i suggest we pose a few different hyptothetical
> sample questions to each other, so that we can see how certain KEYWORDS and
> requirementes affect the answer.
>
> Here's one.
>
> Internal network address range is 1.1.X.0/24 Router 1 has an E0/0 link to
> the backbone (BB1)
>
> Question
> Your network has become extremely slow and you suspect a DOS attack coming
> from BB1.
> Create an acl which will log icmp flood/smurf attacks to your logging
> buffer.
> Create this acl on R1 in a manner which will assist you to distinguish
> between these attacks wherever possible.
>
>
>
>
>
>
>
>
> ________________________________
>
> From: Scott Morris [mailto:swm@emanon.com]
> Sent: Thursday, 24 August 2006 6:09 AM
> To: 'Aamir Aziz'; 'David Mitchell'
> Cc: 'Chris Broadway'; 'Peter Plak'; 'Victor Cappuccio'; 'Dusty'; David
> Redfern (AU); ccielab@groupstudy.com
> Subject: RE: ICMP Flooding vs SMURF Attack---THE BRIANS AND SCOTT
>
>
> I'll stick with the answer of "it depends" :)
>
> in your first one, you are assuming that all links are /24. Which may be
> true, but you'll have to look at your topology to assess that!
> in the second one, it certainly blocks it all, which again may or may not be
> what you want to accomplish.
>
> There is NO SINGLE answer!
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
> #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPExpert VP - Curriculum Development
> IPExpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com
>
>
> ________________________________
>
> From: Aamir Aziz [mailto:aamiraz77@gmail.com]
> Sent: Wednesday, August 23, 2006 3:11 PM
> To: David Mitchell
> Cc: Scott Morris; Chris Broadway; Peter Plak; Victor Cappuccio; Dusty; David
> Redfern (AU); ccielab@groupstudy.com
> Subject: Re: ICMP Flooding vs SMURF Attack---THE BRIANS AND SCOTT
>
>
> Hi all
>
> Many thanks for the all the replies. Ok so if i build the following ACL
> (lets say on edge router) to protect myself from being the REFLECTOR and the
> VICTIM for SMURF/Fraggle attack would this work:
>
> deny icmp any 0.0.0.255 <http://0.0.0.255/> 255.255.255.0
> <http://255.255.255.0/> echo deny icmp any 0.0.0.0 <http://0.0.0.0/>
> 255.255.255.0 <http://255.255.255.0/> echo deny icmp any 0.0.0.255
> <http://0.0.0.255/> 255.255.255.0 <http://255.255.255.0/> echo-reply deny
> icmp any 0.0.0.0 <http://0.0.0.0/> 255.255.255.0 <http://255.255.255.0/>
> echo-reply deny udp any any eq echo deny udp any eq echo any permit ip any
> any
>
> or this one (from
> http://www.cisco.com/en/US/tech/tk59/technologies_tech_note09186a0080149
> ad6.shtml#topic3)
>
> deny icmp any any echo
> deny icmp any any echo-reply
> deny udp any any eq echo
> deny udp any eq echo any
> permit ip any any
>
> Which of them would work? If both then which is appropriate for CCIE lab, if
> neither then what is missing here.
>
> Many thanks
> Aamir
>
>
>
> On 8/23/06, David Mitchell <david.mitchell@centientnetworks.com> wrote:
>
> If my understanding of Smurf attacks is correct, your strategy would
> succeed in stopping you from being the REFLECTOR, but not the
> VICTIM.
>
> If you are the VICTIM of a Smurf attack, the packets you will be
> seeing
> will be unicast icmp echo-reply packets sourced from the REFLECTOR
> to
> your address. This would be because the attacker spoofed your
> address
> range and sent the icmp echo-requests to the reflector's broadcast
> address, resulting in the reflector responding with the echo-reply's
> to
> your addresses.
>
> If my understanding is correct, you would need to filter out icmp
> echo-reply packets on the edge to stop this.
>
> Hopefully I understand this properly. So far I'm a two-time
> Security
> lab failure!!
>
> - Dave
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> Scott Morris
> Sent: Wednesday, August 23, 2006 12:17 PM
> To: 'Aamir Aziz'
> Cc: 'Chris Broadway'; 'Peter Plak'; 'Victor Cappuccio'; 'Dusty';
> 'David
> Redfern (AU)'; ccielab@groupstudy.com
> Subject: RE: ICMP Flooding vs SMURF Attack---THE BRIANS AND SCOTT
>
> If you are looking to stop an attack TO a router, I'd use:
>
> no ip directed-broadcast (on each interface)
> no service udp-small-servers (which will shut down those udp
> ports)
>
> I believe both may be defaults now (Cisco is occasionally nice).
>
> If you have to filter on an edge, which makes more sense, I believe
> both
> Brian and I have offered multiple methods of accomplishing this.
> One is
> not
> necessarily better than another. Below, I lay out the port numbers
> for
> you,
> so build an ACL matching each of those in udp as well as ICMP echo
> coming
> in.
>
> Building the ACL shouldn't be a difficult exercise as you know the
> information below. In the middle of your exam (IMHO) you won't be
> required
> to memorize the multiple ports that a Fraggle attack may go after
> unless
> it
> is mentioned someplace on the DocCD. So build away! Come up
> with one
> and
> let's see what you got!
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> JNCIE
> #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPExpert VP - Curriculum Development
> IPExpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com
>
>
> _____
>
> From: Aamir Aziz [mailto:aamiraz77@gmail.com]
> Sent: Wednesday, August 23, 2006 10:09 AM
> To: swm@emanon.com
> Cc: Chris Broadway; Peter Plak; Victor Cappuccio; Dusty; David
> Redfern
> (AU);
> ccielab@groupstudy.com
> Subject: Re: ICMP Flooding vs SMURF Attack---THE BRIANS AND SCOTT
>
>
> Dear Mr.Brian & Mr.Scott,
>
> Thank you for the valuable input, i think it was really helpfull but
> lets
> say in the exam if they clearly mention that it is a SMURF/Fraggle
> attack
> and we need to stop it using ACL then in your expert opinion what
> ACL
> should
> we use on the router?
>
> Thanks
> Aamir
>
>
> On 8/22/06, Scott Morris <swm@emanon.com> wrote:
>
> Well, look at the two attacks and what they are first.
>
> Smurf is an ICMP-based attack. Typically the echo-request packets
> are
> sent
> TO the subnet-broadcast address. This is simply stopped (and by
> default)
> with "no ip directed-broadcast" on a LAN. Or you can filter on an
> edge
> router closer to the Internet link using an extended ACL.
>
> Being that most Smurf attacks are also from spoofed addresses, "ip
> verify
> unicast reverse-path" or "ip verify unicast source reachable via
> any"
> could
> help. (<--RFC 2267) You could also rate-limit the information, but
> this
> isn't the best solution!
>
> Fraggle is the same type of attack, except that it involves UDP
> packets
> instead of ICMP ones. Typically it's directed at common unix-based
> echo
> ports (7, 13, 17, 19). So the same methods will protect you.
>
> For TCP SYN attacks, that usually involves a bunch of embryonic
> (half-open)
> connections going on. Short of your router(s) monitoring the number
> of
> initial TCP open requests that come in, there's not many good ways
> to do
>
> this! Firewalls (including CBAC) are certainly the best ways, but
> not
> on
> the R&S exam!!!
>
> You may have TCP Intercept on your exam covered by some of the more
> generic
> security features listed on the Blueprint! Look in the same
> security
> command reference where the RPF information is at, and you'll see
> "ip
> tcp
> intercept" for some information on that.
>
> While you could rate-limit with an acl matching "tcp any any syn".
> Like
>
> many things which thing you choose as your solution may depend on
> requirements of the lab!
>
> Just my thoughts...
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> JNCIE
> #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPExpert VP - Curriculum Development
> IPExpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com <http://www.ipexpert.com>
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> Chris Broadway
> Sent: Tuesday, August 22, 2006 11:21 AM
> To: Peter Plak
> Cc: Victor Cappuccio; Dusty; David Redfern (AU); Aamir Aziz;
> ccielab@groupstudy.com
> Subject: Re: ICMP Flooding vs SMURF Attack---THE BRIANS AND SCOTT
>
> Group,
>
> Can we get the "Brians" and/or Scott to give us their opinion on the
> definitive ACL to log smurf, fraggle, and TCP syn attacks? I think
> everyone
> has an opinion but have not heard from the ones I consider to be the
> most
> trusted sources.
>
> -Broadway
>
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
> <http://www.groupstudy.com/list/CCIELab.html >
>
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
>
> ****************************************************************************
> *
> *
> - NOTICE FROM DIMENSION DATA AUSTRALIA
> This message is confidential, and may contain proprietary or legally
> privileged information. If you have received this email in error, please
> notify the sender and delete it immediately.
>
> Internet communications are not secure. You should scan this message and any
> attachments for viruses. Under no circumstances do we accept liability for
> any loss or damage which may result from your receipt of this message or any
> attachments.
> ****************************************************************************
> *
> *
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Fri Sep 01 2006 - 15:41:58 ART