Security Basics: RE: Why bandwidth consuming ddos attack using only udp or icmp?

["Ajay Tikoo" <ajay () printwire org>]

I agree with what David has written.

I just want to point out that instead of filtering all udp at the border
router, why would you not filter all "unwanted" udp packet (based on source
and destination port). For example, in order to allow DNS pass through, you
would accept udp traffic with source or destination port of 53.

Ajay Tikoo

-----Original Message-----
From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On
Behalf Of David Gillett
Sent: Friday, February 29, 2008 11:51 AM
To: 'MontyRee'; 
Subject: RE: Why bandwidth consuming ddos attack using only udp or icmp?

> So, some network administrator said that he filtered all udp 
> and icmp just against the bandwidth consuming ddos attack at 
> the border router.
> (Surely some problems would be happen..dns..somethinf like that)
  Presumably he made an exception for DNS, and perhaps NTP.

  Note that the bandwidth bottleneck is typically outside the border router,
so filters on that router only apply after the bandwidth has been
consumed....

> Is it impossible or ineffective using tcp for bandwidth 
> consuming attack in the point of attacker?
> anyone who saw the bandwidth consuming attack using tcp?
  It's not impossible, but it's extra work, and reveals the attacker's IP
address to anyone who detects the attack.  (Or at least one or more
addresses under the attacker's control.)

  In your case, the TCP portion of the attack is probably trying to 
exhaust half-open connection entries (SYN flood) rather than bandwidth.
He can use spoofed source addresses for that.

David Gillett

 

> -----Original Message-----
> From: listbounce () securityfocus com 
> [mailto:listbounce () securityfocus com] On Behalf Of MontyRee
> Sent: Thursday, February 28, 2008 6:52 PM
> To: security-basics () securityfocus com
> Subject: Why bandwidth consuming ddos attack using only udp or icmp?
>
>
>
> Hello, list.
>
> I have operated network in my company and recently I have 
> experienced some ddos attack(inbound) on my network.
>
> It seems that the ddos attack was divided in two
>
> first, the bandwidth consuming attack was all consist of udp 
> or icmp using big size packet(about 1500 byte).
> second tcp based attack for example http(80/tcp) is mostly 
> creates lots of pps using small size packet(about 40 byte )
>
> So, some network administrator said that he filtered all udp 
> and icmp just against the bandwidth consuming ddos attack at 
> the border router.
> (Surely some problems would be happen..dns..somethinf like that)
>
> and I have one question.
>
> Is it impossible or ineffective using tcp for bandwidth 
> consuming attack in the point of attacker?
> anyone who saw the bandwidth consuming attack using tcp?
>
>
> Thanks in advance.
>
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