Re: DNS Floods to personal firewalls

[Thomas Roessler <roessler () does-not-exist org>]

Last night, I could observe a pattern similar (but not identical!) 
to the one you report: There was a whole slew of TCP packets to port 
53, all with the SYN and ACK bits set. (These packets were cought by 
the stateful packet filter of linux 2.4.)

I looked the list of source IP addresses you compiled, and found 
that 21 of them are occuring in my logs, too.

The same characteristic also applies to the logs at 
http://members.iinet.net.au/~paulhng/lrp/kernlog.txt which David 
posted, and which are 10 days old. (!)

On de.comp.security.firewall, "Michael Linke" <ml () globetrotter de> 
has been talking about what he describes as "little DDoS attacks 
(20-30 clients) with SYN ACK packets to port 53", which looks like 
he is seeing the same activities we are observing.

My own logs are attached.  Also, here's a summary of the IP 
addresses and where they occur.  keith means that the address was in 
your list, tifa means that it was in kernlog.txt (it's the host name 
there), and sobolev means that it was in my logs (host name once 
again).

140.239.176.162         keith   sobolev tifa    
165.121.70.75           keith                   *
194.205.125.26          keith   sobolev tifa    
194.213.64.150          keith   sobolev tifa    
202.139.133.129         keith   sobolev tifa    
203.194.166.182         keith   sobolev tifa    
203.208.128.70          keith   sobolev tifa    
207.55.138.206          keith   sobolev tifa    
208.184.162.71          keith   sobolev tifa    
209.249.97.40           keith   sobolev tifa    
212.23.225.98           keith   sobolev tifa    
212.78.160.237          keith           tifa    *
212.78.164.193                  sobolev         *
216.220.39.42           keith   sobolev tifa    
216.33.35.214           keith   sobolev tifa    
216.34.68.2             keith   sobolev tifa    
216.35.167.58           keith   sobolev tifa    
62.23.80.2              keith   sobolev tifa    
62.26.119.34            keith   sobolev tifa    
63.209.147.246          keith   sobolev tifa    
64.14.200.154           keith   sobolev tifa    
64.37.200.46            keith   sobolev tifa    
64.56.174.186           keith   sobolev tifa    
64.78.235.14            keith   sobolev tifa    

Note, in particular, that a whole lot of these addresses are 
occuring in all three log files.  However, one IP only occured on 
sobolev, one IP is only included with Keith's list, and one IP was 
observed by Keith and on tifa, but not on sobolev.

Anyway, I don't have any conclusions to offer on this, but maybe 
soemone else can offer reasonable ideas.


On 2001-05-15 09:50:06 -0400, Keith.Morgan wrote:
> Mailing-List: contact incidents-help () securityfocus com; run by ezmlm
> From: "Keith.Morgan" <Keith.Morgan () Terradon com>
> To: "'focus-linux () securityfocus com'" <focus-linux () securityfocus com>
> Cc: "'incidents () securityfocus com'" <incidents () securityfocus com>
> Subject: RE: DNS Floods to personal firewalls
> Date: Tue, 15 May 2001 09:50:06 -0400
> X-Mailer: Internet Mail Service (5.5.2650.21)
>
> We've been seeing these as well.  But not just to personal firewalls.  I've
> seen them on cable modems, dsl lines, and corporate T-1's.   
>
> I'm cross-posting this because I've seen references to this type of activity
> on multiple lists.
>
> I'm a bit baffled by this.  The source port is always 53, with a random
> destination port.  And they appear to be replies to me as well.  A
> possibility is that we're being used as decoy addresses in some sort of
> scanning.  However, since the addresses are *SO* random, this tends to rule
> out nmap as a scanner using --randomize-hosts.  Nmap will randomize, but
> when fed a really large network block to scan, it will scan within three or
> so class C networks at a time.  
>
> Are there other scanning tools with the ability to use spoofed decoy
> addresses, yet provide better randomization than nmap when scanning?
>
> Keith T. Morgan
> Chief of Information Security
> Terradon Communications
> keith.morgan () terradon com
> 304-755-8291 x142
>
>
> > -----Original Message-----
> > From: Ben Alexander [mailto:balexander () pmg net]
> > Sent: Monday, May 14, 2001 10:25 AM
> > To: 'n9ubh () callsign net'
> > Cc: 'focus-linux () securityfocus com'
> > Subject: RE: DNS Floods to personal firewalls
> >
> >
> > I received these as well, and I know a few others that 
> > receive them also.
> > Using arin whois, here is what I put together:
> >
> > [140.239.176.162/17221] HarvardNet
> > [165.121.70.75/64551]   Earthlink
> > [194.205.125.26/41123]  European Regional Internet Registry
> > [194.213.64.150/47642]  European Regional Internet Registry
> > [202.139.133.129/41595] Asia Pacific Network Information Center
> > [203.194.166.182/38808] Asia Pacific Network Information Center
> > [203.208.128.70/12235]  Asia Pacific Network Information Center
> > [207.55.138.206/61929]  "Verio, Inc."
> > [208.184.162.71/53567]  Abovenet Communications
> > [209.249.97.40/45714]   Abovenet Communications
> > [212.23.225.98/57974]   European Regional Internet Registry
> > [212.78.160.237/29368]  European Regional Internet Registry
> > [216.220.39.42/21602]   "Myna Communications, Inc."
> > [216.33.35.214/21092]   Exodus Communications
> > [216.34.68.2/45906]     Exodus Communications
> > [216.35.167.58/32470]   Exodus Communications
> > [62.23.80.2/55543]      European Regional Internet Registry
> > [62.26.119.34/56523]    European Regional Internet Registry
> > [63.209.147.246/54734]  Level 3 Communications
> > [64.14.200.154/32735]   Exodus Communications
> > [64.37.200.46/65042]    Exodus Communications
> > [64.56.174.186/14237]   Exodus Communications
> > [64.78.235.14/17768]    "Verado, Inc. (Firstworld Communications)"
> >
> > > -----Original Message-----
> > > From: ssrat () MAILBAG COM [mailto:ssrat () MAILBAG COM]
> > > Sent: Sunday, May 06, 2001 10:24 PM
> > > To: FOCUS-LINUX () SECURITYFOCUS COM
> > > Subject: DNS Floods to personal firewalls
> > > 
> > > 
> > > There seems to be lots of these happening.  They appear to be some
> > > kind of DNS replies, but are getting rejected by the 
> > firewall - these
> > > reports are coming from the Linux Router Project (LRP) list.
> > > 
> > > I've asked for a tcpdump to be sent, as I've not seen 
> > these; could it
> > > be a DNS server somewhere was taken over, or some kind of 
> > attack tool
> > > generates the same spoofed addresses?
> > > 
> > > So far the main report details are the reject lines from ipchains in
> > > /var/logs/messages.
> > > 
> > > Here is a portion one person posted:
> > > 
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 208.184.162.71:34387 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=236
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 202.139.133.129:47571 203.59.110.14:53 L=44 S=0x00 I=0 
> > F=0x0000 T=241
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 203.208.128.70:16146 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=247
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 194.205.125.26:42786 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=242
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 209.249.97.40:34126 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=236
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 216.33.35.214:15928 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=237
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 140.239.176.162:11843 203.59.110.14:53 L=44 S=0x00 I=0 
> > F=0x0000 T=237
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 216.34.68.2:38839 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=237
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 207.55.138.206:24678 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=238
> > > (#37)
> > > May  6 14:39:57 tifa kernel: Packet log: input DENY ppp0 PROTO=6
> > > 216.35.167.58:24169 203.59.110.14:53 L=44 S=0x00 I=0 F=0x0000 T=237
> > > (#37)
> > > 
> > > He has the entire thing in an URL:
> > > http://members.iinet.net.au/~paulhng/lrp/kernlog.txt
> > > 
> > > It also appears that the same IPs are reported over and over again.
> > > It has the markings of some kind of tool I think - but I'm new at
> > > this.
> > > 
> > > 
> > > --
> > > David Douthitt
> > > UNIX Systems Administrator
> > > HP-UX, Unixware, Linux
> > > n9ubh () callsign net
> > > 

--
Thomas Roessler                        http://log.does-not-exist.org/

Attachment: sobolev.txt
Description: