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RE: Yet another thread on the legality of port scanning
From: "Yvan Boily" <yboily () seccuris com>
Date: Thu, 18 Mar 2004 12:29:56 -0600

Authorized users are told they are authorized users.


Perhaps I'm not aware of it, but is there an "authorized 
database on the internet?  I must have missed that.
A far more important distinction to be made here is that any service which
requires authorization should explicitly advertise the requirement for

If you are running a service that is available to the public (i.e. listening
on the internet) then if you do not wish it to be accessible to the public
you must implement a mechanism of locking the door.  The analogy of a port
being a door is not accurate; a port is exactly that, a portal into a
system.  The access control mechanism implemented to control access would be
the door.  Connecting to the port is the equivalent of identifying if there
is a way into a building.  If you complete the connection you are attempting
to open the door.  This is the where the key concept of security comes in.
If the user attempts to open the door it can be locked or unlocked.  If the
door is locked then it can be assumed that a user is not authorized unless
properly authenticated.

If you do not implement a mechanism of controlling who can open the door
then you have made a publicly available service publicly accessible.  If the
user does not have legitimate access they can attempt to circumvent
controls.  This is the distinction between an attack and a port scan.


Yvan Boily
Information Security Analyst

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