RE: login banners

["Bernie, CTA" <cta () hcsin net>]

At first glance one would say that login banners are analogous 
to someone putting a "do not trespass" sign out on their lawn. 
However, there is a significant difference in that the person 
attempting computer access could be using a legitimate auto 
login program that prevents the user from seeing your banner. 
Accordingly, I would imagine that a grounded legal argument 
could be made to establish that the user was using an 
automated tool and consequently in good faith did not know. In 
my opinion, the weight of such an argument may be light but 
effective in a civil litigation, it is probably sufficient to establish 
reasonable doubt in a criminal prosecution. 

> From a security point of view, my practice is not to use 
banners on systems that could be accessed via public 
networks, as doing so alerts a would be attacker that there may 
be something valuable awaiting within. In addition, I believe that 
using banners also elevate potential risks of system finger 
printing or exploitation of the login program. Conversely, I do 
believe in using banners on internal systems which state 
something like "Only authorized users may attempt or login to 
this system. Be aware that unauthorized login or attempts are a 
violation of XYZ Computer Security Policy, and consequently 
you may be terminated from employment, and/or civilly or 
criminally prosecuted." 


On 19 Feb 2003, at 16:37, Brearley, Kyle wrote:

> i work for a major bank and we use warning banners, login banners
> etc for that reason.  it is possible for attackers to plead
> ignorance in that they were unaware they were on a system that
> prohibited unauthorized access.  routers and the like should
> definitely have them.  same goes for windows systems.  it takes a
> matter of 2 minutes to set it up, it's like why not? better to be
> safe than sorry.
>
> KYLE
>
> -----Original Message-----
> From: Patrick Kingi [mailto:Patrick.Kingi () nz logical com]
> Sent: Monday, February 17, 2003 7:55 PM
> To: pen-test () securityfocus com
> Subject: login banners
>
>
> Greetings all,
>
> It has been standard practice to ensure systems ensure their
> login banners warn the users that unauthorised access is not
> allowed, your activity may be logged etc...
>
> A client has asked if there is any evidence that this really
> matters. I heard a story once upon a time that a hacker did not
> get prosecuted because the login banner said something like
> "Welcome to your friendly neighborhood computer". Is this an
> urban legend?
>
> Does anyone have any evidence that the login banner has been used
> in court?
>
> Any help would be appreciated.
>
> regards,
> Patrick
>
>
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> Do you know the base address of the Global Offset Table (GOT) on
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-


-
****************************************************
Bernie 
Chief Technology Architect
Chief Security Officer
cta () hcsin net
Euclidean Systems, Inc.
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Do you know the base address of the Global Offset Table (GOT) on a Solaris 8
box?
CORE IMPACT does.
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