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	Tue, 1 Jul 1997 22:13:58 +0300 (EEST)
Date: Tue, 1 Jul 1997 22:13:58 +0300 (EEST)
From: Sergey Pukach <pss@gloom.te.net.ua>
Message-Id: <199707011913.WAA00442@gloom.te.net.ua>
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To: freebsd-questions@freebsd.org
Subject: Security hole ?
Cc: kvn@gloom.te.net.ua, vlad@nobulus.tn.odessa.ua
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Hi.

I have two ISP, one of which running FreeBSD and assign static IP
to all users. For connection I'm using ppp by Toshiharu OHNO.
Playing wiht /etc/ppp/ppp.conf I'm found amazing (for me) feature.
This is string from ppp.conf:

add ifaddr a.b.c.d  0

So, remote server can use any IP and my IP should be a.b.c.d
If instesd of a.b.c.d I substitute real IP of one of my ISP server
I can declare myself as another machine. During such connection
I have received a lot of mail which is not intended to be mine.
I think skilful hacker can use this in another way. So, how
ISP can avoid such unproper connections?

pss

// Sergey Pukach
// pss@te.net.ua