Check Point Advisories

Microsoft SMB Invalid Write Mode Evasion Technique

Vulnerability
Protection

Check Point Reference:	SBP-2010-32
Date Published:	25 Nov 2010
Severity:	Critical
Last Updated:	Sunday 09 June, 2013
Source:
Protection Provided by:	Security Gateway R81, R80, R77, R75, R71, R70, R65
Who is Vulnerable?
Vulnerability Description	The SMB Protocol is a network file sharing protocol that is implemented in Microsoft Windows. There are many known vulnerabilities in applications based on the SMB protocol. Though IDS and IPS devices have signatures to detect attacks exploiting these vulnerabilities, these devices can be evaded. SMB requests with invalid flags are usually discarded by the receiving host. Correct reassembly of SMB conversations requires that the inspection device discards the same payload as the receiving server. Attackers may use SMB write requests containing an invalid Write Mode and random payload as an IDS/IPS evasion technique.

Protection Overview

This protection will detect and block malformed SMB requests attempting to exploit this vulnerability.

In order for the protection to be activated, update your Security Gateway product to the latest IPS update. For information on how to update IPS, go to SBP-2006-05, click on Protection tab and select the version of your choice.

Security Gateway R80 / R77 / R75 / R71 / R70 / R65

In the IPS tab, click Protections and find the Microsoft SMB Invalid Write Mode Evasion Technique protection using the Search tool and Edit the protection's settings.
Install policy on all Security Gateways.

This protection's log will contain the following information:

Attack Name: Windows SMB Protection Violation.
Attack Information: Microsoft SMB invalid write mode evasion technique