Re: IP number question

From: Lassi Hippeläinen (lahippel_at_ieee.orgies.invalid)
Date: 01/27/05 

Date: Thu, 27 Jan 2005 07:08:04 GMT

Michael J. Pelletier kirjoitti:
> manmar@h2009.com wrote:
>
>
>>I recently came across a NG post that mentioned a friend of mine.
>>Because of the subject of the post I checked the IP number of the
>>posting. The IP number matches that of another individual I know but
>>who would not make such postings and also hardly is ever on their
>>computer. It is possible for one person to use another person's IP
>>address to post to a newsgroup? How can this be possible?
>>Any feedback would be appreciated with thanks.
>
>
> Well, it depends. Does the other person have remote access to your friends
> PC?
>
> Also, if they are not on the same subnet, the other guy CAN NOT use his IP.
> Remember IP 101. For this guy to forge your friends IP address, he must
> have a route out and back for that IP address. If the other guy is not on
> the same LAN, he does not have a route back....He can forge DOS type
> attacks but can not forge a duplex communication. A duplex communication is
> require to post to a news group.

No. Read NAT 101. Or DHCP 101.

> So, what I am saying is this. If the other guy does not have remote access
> capability and he is NOT on the same LAN that answer is no.

You may be using the same IP as someone else at some other time, simply
because most IP addresses are allocated dynamically. All that is needed
is that you are in the same subnet as the other user.

If you are in a private address network (e.g. 10.x.y.z) it is certain
that someone else somewhere else has the same address, probably even at
the same time, but a NA(P)T separates you from each other.

-- Lassi

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