If you want full control of network read/writes use
libnet/libpcap.. have a look at tcpdump.org.. 

Using libnet/libpcap you can write directly to the
wire.

--- Paulo Abrantes <[EMAIL PROTECTED]> wrote:
> Hello Vik,
> 
> What the attacker does is not allowing the Kernel to
> fill in the IP datagram 
> from the packet he's spoofing, and filling it by
> himself/herself. 
> How can (s)he do that? 
> Well, the best way I know, and probably is the way
> that land.c (that you mention) 
> uses (I do do not know the source of that program)
> is creating a RAW socket. 
> Then using a function called setsocketop() enabling
> the option IP_HDRINCL which 
> allows you to include your own IP Header. This way
> it's you that create the all
> the IPheader including  IP Source Address.
> 
> For further information give a look at raw(7) man
> page.
> 
> Regards, 
> 
> P. Abrantes 
> 
> On Sat, 9 Nov 2002 13:10:11 -0700
> "Vik Evans" <[EMAIL PROTECTED]> wrote:
> 
> > My question is this: how does an attacker
> accomplish modifying a packet and
> > sending it; such as in a land.c attack - how does
> he modify the packet to
> > reflect the victim's source and destination IP and
> then send it onto the
> > wire?
> > 
> > -----Original Message-----
> > From: Fuchs Bernhard
> [mailto:[EMAIL PROTECTED]]
> > Sent: Tuesday, November 05, 2002 5:58 AM
> > To: 'vijay vikram shreenivos';
> [EMAIL PROTECTED]
> > Subject: AW: Smurf ,land attacks
> > 
> > 
> > Hi there!
> > 
> > with "IP spoofing" you give a different source
> address to the packet. the
> > address is different to your real address. You do
> this for cloaking your
> > scan or if company A scans company B and spoofes
> the address of company c.
> > so company b thinks it is company c scanning them!
> o.k.? but company a will
> > not get any results back! this is mostly to cloak
> your own scan.
> > 
> > Smurf is a DoS-Attack (denial of service)
> > You Amplifi your ping through a big network. You
> ping a subnet like
> > x.x.x.255 with an SPOOFED IP-Adress and every
> computer on that big net
> > responses to the poor little machine  that has the
> IP-Adress. Think of class
> > B subnet with a few hosts reply to a ADSL
> connected machine... 1500kb
> > download and 196 kb upload :-)
> > 
> > land attack is a TCP SYN packet that has the ip
> address and port number for
> > the source set to the same as the ip address and
> port number for the
> > destination. the server connects to itself.
> > 
> > 
> > any comments?
> > 
> > by the way, google knows it too :-)
> > 
> > Mit freundlichen Gr��en/ sincerely yours
> > 
> > 
> > Bernhard Fuchs
> > Junior System-Engineer
> > IT-Infrastruktur
> > 
> > ITELLIUM
> > Systems & Services GmbH
> > F�rther Stra�e 205
> > 90429 N�rnberg
> > 
> > Tel.:   +49-911-14-27321
> > Fax:    +49-911-14-22016
> > mailto:[EMAIL PROTECTED]
> > http://www.itellium.com
> > 
> > This email is confidential. If you are not the
> intended recipient, you must
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> it. If you have received
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> > and any attachments is sent.
> > 
> > 
> > 
> > -----Urspr�ngliche Nachricht-----
> > Von: vijay vikram shreenivos
> [mailto:[EMAIL PROTECTED]]
> > Gesendet: Samstag, 2. November 2002 08:15
> > An: [EMAIL PROTECTED]
> > Betreff: Smurf ,land attacks
> > 
> > 
> > Hi list,
> > 
> > 
> > Can someone give the EXACT differences btw
> > 
> > SMURF
> > LAND
> > and IP soofing attacks.
> > 
> > karpagamekapalidurgau
> >
>
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