RE: Packets from 255.255.255.255(80) (was: Packet from port 80 with spoofed microsoft.com ip)

["David Gillett" <gillettdavid () fhda edu>]

1.  It seems to me that packets with that destination address 
are going to be routable to your network from only a small number 
of nearby networks -- probably only the local network itself.

Conclusion:  The random source addresses are spoofed.

Test:  Look at the source MAC addresses.  If these are all the
MAC address of your gateway router's interface, then someone has
found a way to route into your network (or the MAC address is 
*also* being spoofed...).  Otherwise, that should have good odds
of leading you to the internal machine that is spewing these.

2.  You haven't said whether these were TCP or UDP, but since 
TCP to a broadcast address can't possibly hope to ever establish a 
connection, either the person behind this doesn't understand how it
works (improving the odds that the MAC address isn't spoofed...),
or the packets must be self-contained attacks (more likely with
UDP, although I don't know why anything would ever be listening on
UDP port 80....

David Gillett


> -----Original Message-----
> From: greg () optionsinternet com [mailto:greg () optionsinternet com]
> Sent: January 30, 2003 13:29
> To: incidents () securityfocus com
> Cc: hasan () hasan org; tomek-incid () lodz tpsa pl
> Subject: RE: Packets from 255.255.255.255(80) (was: Packet 
> from port 80
> with spoofed microsoft.com ip)
>
>
> Today we have been receiving on average 380,000 requests an hour TO
> 255.255.255.255 FROM random IPs. I performed a reverse DNS query on a
> sample of 200 hosts, 2 of which came back with hostnames. A 
> ping scan of
> the very same 200 hosts showed that only around 20 were *active*.
>
> I contacted our ISP and was told that this traffic was "normal".
>
> Has anyone else seen any similar requests?
>
> Regards
>
> Greg Bolshaw
>
>
> Original Message:
> -----------------
> From: Tomasz Papszun tomek-incid () lodz tpsa pl
> Date: Thu, 30 Jan 2003 19:03:51 +0100
> To: incidents () securityfocus com
> Subject: Packets from 255.255.255.255(80) (was: Packet from 
> port 80 with
> spoofed microsoft.com ip)
>
>
> On Thu, 30 Jan 2003 at 14:31:36 +1100, Keith Owens wrote:
> > On Wed, 29 Jan 2003 21:46:53 +1100, 
> > Michael Rowe <mrowe () mojain com> wrote:
> > > I received a packet on my cable modem today, allegedly from
> > > microsoft.com: 
> > >
> > > 18:41:35.663374 207.46.249.190.80 > my.cable.modem.ip.1681:
> S866282571:866282571(0) ack 268566529 win 16384 <mss 1460>
> > I am seeing a lot of sync/ack packets from port 80 to non-existent
> > addresses on my networks.  Somebody is spoofing source addresses to
> > attack hosts, we are just innocent victims.  When will ISPs 
> learn that
> > they should filter their customer's packets to prevent 
> spoofing?  I am
> > even seeing syn/ack packets from 255.255.255.255:80!
>
> Similarly at my networks.
> Yesterday evening (Jan 29 21:10 GMT+1) a very noticeable 
> stream of such
> packets started to come into my networks.
>
> All are TCP, from 255.255.255.255(80), destined to various random
> addresses (even not used) to various port numbers.
>
> This appearance is very noticeable. Before yesterday, single packets
> from 255.255.255.255 were coming in rate about one for three weeks.
> Since yesterday there have been about 1680 for 22 hours.
>
> -- 
>  Tomasz Papszun   SysAdm @ TP S.A. Lodz, Poland  | And it's only
>  tomek () lodz tpsa pl   http://www.lodz.tpsa.pl/   | ones and zeros.
>
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