From: Peter Plak (plukkie@gmail.com)
Date: Mon Aug 21 2006 - 05:35:21 ART
David,
You're 100% right about missing the unicast replies in the .255 and .0
subnets. But the correct answer is maybe hide in the question.
My exam question was titled "log icmp attack / smurf attack".
Smurf is often an attack to those .255 and .0 addresses.
ICMP flooding often just to a unicast.
Fragle with udp.
So again, it's unsure what they want to see.
In my question, I had to only log. My list was not allowed to block.
I did not log icmp to unicast addresses, and i also logged udp. Maybe that;s
why I didn't get the points.
gr
On 8/21/06, David Redfern (AU) <David.Redfern@didata.com.au> wrote:
>
>
> Only problem I see is with the icmp echo-reply lines.
>
> deny icmp any 0.0.0.255 255.255.255.0 echo-reply
> deny icmp any 0.0.0.0 255.255.255.0 echo-reply
>
> If you are the end target of the attack receiving echo-replies from the
> reflector network then this echo reply would/could be destined for host
> addresses in your network. A server for example the DOS is targeting.
> The acl only block echo-replies to the 0 or 255 address, which is not
> where the target will be.
>
> Maybe you have to block icmp any any echo-reply coming in but this this
> stops you from being able to ping the backbone. Only way around this I
> know is to to a reflective acl.
>
> If you get an answer to this one please let me know
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Peter Plak
> Sent: Monday, 21 August 2006 7:47 AM
> To: Aamir Aziz
> Cc: ccielab@groupstudy.com
> Subject: Re: ICMP Flooding vs SMURF Attack
>
> Is it possible to have a udp with source echo, sourced from the network
> (
> x.x.x.0) or broadcast (x.x.x.255)?
> The source udp echo is probably from the reflector, so it's replied to
> the destination network or broadcast I would presume.
>
> Then I would say for the udp streams it's:
>
> deny udp any 0.0.0.255 255.255.255.0 eq echo deny udp any 0.0.0.0
> <http://0.0.0.255/> 255.255.255.0 eq echo deny udp any eq echo
> 0.0.0.255 255.255.255.0 deny udp any eq echo 0.0.0.0 <http://0.0.0.255/>
> 255.255.255.0
>
> gr
>
>
>
>
> On 8/20/06, Aamir Aziz <aamiraz77@gmail.com> wrote:
> >
> > Yes i agree with you that the UDP source is missing here, but the
> > question is what is most suitable or lets say what is required in the
> > lab, how about if we go for something like this:
> >
> > deny icmp any 0.0.0.255 255.255.255.0 echo deny icmp any 0.0.0.0
> > 255.255.255.0 echo deny icmp any 0.0.0.255 255.255.255.0 echo-reply
> > deny icmp any 0.0.0.0 255.255.255.0 echo-reply deny udp any 0.0.0.255
>
> > 255.255.255.0 eq echo deny udp 0.0.0.255 255.255.255.0 eq echo any
> > deny udp any 0.0.0.0 255.255.255.0 eq echo deny udp 0.0.0.0
> > 255.255.255.0 eq echo any permit ip any any
> >
> > this one makes any sense?
> >
> > Thanks
> > Aamir
> >
> > > >
> >
> >
> > On 8/20/06, Peter Plak <plukkie@gmail.com> wrote:
> > >
> > > Hi Aziz,
> > >
> > > I have also spent lot of time to this task. I found a link which
> > > enters the explanation of smurf / fragle and protection best so far.
> > >
> > > http://www.windowsecurity.com/whitepaper/Characterizing_and_Tracing_
> > > Packet_Floods_Using_Cisco_Routers.html
> > >
> > > <http://www.windowsecurity.com/whitepaper/Characterizing_and_Tracing
> > > _Packet_Floods_Using_Cisco_Routers.html+>
> > >
> > > If I look at your list, I would say, almost there. What in my
> > > opinion misses is the udp source eq echo.
> > > I would replace the udp lines with any any. Cause udp echo is rarely
>
> > > used nowadays, it's likely that you will have many hits compared to
> icmp.
> > >
> > > So, I think the list totally will be then:
> > > deny icmp any 0.0.0.255 255.255.255.0 echo deny icmp any 0.0.0.0
> > > 255.255.255.0 echo deny icmp any 0.0.0.255 255.255.255.0 echo-reply
>
> > > deny icmp any 0.0.0.0 255.255.255.0 echo-reply deny upd any any eq
> > > echo deny upd any eq echo any permit ip any any
> > >
> > > What you think?
> > >
> > >
> > > On 8/20/06, Aamir Aziz < aamiraz77@gmail.com > wrote:
> > >
> > > > Hi there ppl
> > >
> > > I just wanted to clear something, if the tast says that certain
> > > router is experiencing attack via ICMP and UDP flooding does it mean
>
> > > SMURF ATTACK?
> > >
> > > and would the following ACL work to mitigate this flooding issue?
> > >
> > > deny icmp any 0.0.0.255 255.255.255.0 echo deny icmp any 0.0.0.0
> > > 255.255.255.0 echo deny icmp any 0.0.0.255 255.255.255.0 echo-reply
> > > deny icmp any 0.0.0.0 255.255.255.0 echo-reply deny upd any
> > > 0.0.0.255 255.255.255.0 echo deny upd any 0.0.0.0 255.255.255.0 echo
>
> > > permit ip any any
> > >
> > > Thanks
> > > Aamir
> > >
> > > ____________________________________________________________________
> > > ___ Subscription information may be found at:
> > > http://www.groupstudy.com/list/CCIELab.html
>
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