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RE: Nessus Scan
From: "Craig Wright" <Craig.Wright () bdo com au>
Date: Fri, 17 Aug 2007 05:16:41 +1000

Hello,
No actually you are incorrect. PCI-DSS is not pass/fail. It is:
   - Pass
   - Scan issue found - adequate compensating controls exist
   - Compensating controls exist but are inadequate
   - Fail
Either of the top 2 are acceptible.
 
As for the IPS, Page 4 - Security Scanning Procedures v 1.1
"13. Arrangements must be made to configure the intrusion detection system/intrusion prevention system (IDS/IPS) to 
accept the originating IP address of the ASV. If this is not possible, the scan should be originated in a location that 
prevents IDS/IPS interference"

The idea is that the scan should test the underlying controls and not be solely reliant on the IDS/IPS device. The 
scanning vendor has to have you add them as a trusted host or filter your IP for the scan - it is a part of the test - 
it is a part of the compliance requirement. The PCI standard is designed to ensure that your site meets the minimum 
without the IPS. The IPS may then in some cases be a compensating control.
 
You are allowed (and required) to log the scan - so IDS is ok in sniffer mode, but it is not allowed to interfer with 
the scan in any shape or form.
 
And if you are reliant on the IDS/IPS alone to stop the scan, then as these are generally signiture based devices, you 
are open to new attacks.Hence the requirement to scan sans IPS.
 
Craig



Craig Wright
Manager of Information Systems

Direct : +61 2 9286 5497
Craig.Wright () bdo com au
+61 417 683 914

BDO Kendalls (NSW)
Level 19, 2 Market Street Sydney NSW 2000
GPO BOX 2551 Sydney NSW 2001
Fax +61 2 9993 9497
www.bdo.com.au

Liability limited by a scheme approved under Professional Standards Legislation in respect of matters arising within 
those States and Territories of Australia where such legislation exists.

The information in this email and any attachments is confidential.  If you are not the named addressee you must not 
read, print, copy, distribute, or use in any way this transmission or any information it contains.  If you have 
received this message in error, please notify the sender by return email, destroy all copies and delete it from your 
system. 

Any views expressed in this message are those of the individual sender and not necessarily endorsed by BDO Kendalls.  
You may not rely on this message as advice unless subsequently confirmed by fax or letter signed by a Partner or 
Director of BDO Kendalls.  It is your responsibility to scan this communication and any files attached for computer 
viruses and other defects.  BDO Kendalls does not accept liability for any loss or damage however caused which may 
result from this communication or any files attached.  A full version of the BDO Kendalls disclaimer, and our Privacy 
statement, can be found on the BDO Kendalls website at http://www.bdo.com.au or by emailing administrator () bdo com au 

BDO Kendalls is a national association of separate partnerships and entities.

________________________________


From: listbounce () securityfocus com on behalf of Erin Carroll
Sent: Thu 16/08/2007 8:16 AM
To: Craig Wright; mikef () everfast com
Cc: security-basics () securityfocus com
Subject: RE: Nessus Scan



This is incorrect.

Remember, PCI external quarterly scanning for compliance is required in 11.2
of the PCI guidelines to ascertain the effectivess and PASS/FAIL status of
your security controls around customer CC data and PII. This includes the
IPS/IDS/FW systems. Disabling IPS/IDS or other tools would almost guarantee
a FAIL status report. You might as well turn off your firewalls too while
you're at it. If your Approved Security Vendor is requiring that you do turn
off IPS etc I would strongly suggest finding another ASV.


--
Erin Carroll
Moderator
SecurityFocus pen-test list
"Do Not Taunt Happy-Fun Ball"


-----Original Message-----
From: listbounce () securityfocus com
[mailto:listbounce () securityfocus com] On Behalf Of Craig Wright
Sent: Wednesday, August 15, 2007 12:48 PM
To: mikef () everfast com
Cc: security-basics () securityfocus com
Subject: RE: Nessus Scan

Why is the port open ?

Remember that you have to disable all IPS and such tools
before the scan for the scan vendor.



Craig Wright
Manager of Information Systems

Direct : +61 2 9286 5497
Craig.Wright () bdo com au
+61 417 683 914

BDO Kendalls (NSW)
Level 19, 2 Market Street Sydney NSW 2000 GPO BOX 2551 Sydney
NSW 2001 Fax +61 2 9993 9497 www.bdo.com.au

Liability limited by a scheme approved under Professional
Standards Legislation in respect of matters arising within
those States and Territories of Australia where such
legislation exists.

The information in this email and any attachments is
confidential.  If you are not the named addressee you must
not read, print, copy, distribute, or use in any way this
transmission or any information it contains.  If you have
received this message in error, please notify the sender by
return email, destroy all copies and delete it from your system.

Any views expressed in this message are those of the
individual sender and not necessarily endorsed by BDO
Kendalls.  You may not rely on this message as advice unless
subsequently confirmed by fax or letter signed by a Partner
or Director of BDO Kendalls.  It is your responsibility to
scan this communication and any files attached for computer
viruses and other defects.  BDO Kendalls does not accept
liability for any loss or damage however caused which may
result from this communication or any files attached.  A full
version of the BDO Kendalls disclaimer, and our Privacy
statement, can be found on the BDO Kendalls website at
http://www.bdo.com.au or by emailing administrator () bdo com au 

BDO Kendalls is a national association of separate
partnerships and entities.

________________________________


From: listbounce () securityfocus com on behalf of mikef () everfast com
Sent: Thu 16/08/2007 12:31 AM
To: security-basics () securityfocus com
Subject: Nessus Scan



After a recent external PCI Compliant scan one of my web
servers failed because the scanner determine that  "a port
was open at the beginning of the scan, and is now closed...".
 I've tried all sorts of things to get this corrected the
results remain. I talked with our scanning vendor they don't
seem to have answer as to how to correct the problem. When I
do a Nessus Scan on the site, Nessus reports the issue as a
security note and risk factor of '0', however the my PCI
scanning vendor reports the problem as a risk factor of 4
thus causing the server to fail the scan and resulting a
non-compliance report.

I haven't been able to find anything on how to address this
issue. Where should i look to resolve this problem



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