Check Point Advisories

DCE-RPC Big Endian Evasion Technique

Vulnerability
Protection

Check Point Reference:	SBP-2010-31
Date Published:	25 Nov 2010
Severity:	High
Last Updated:	Thursday 25 November, 2010
Source:
Protection Provided by:	Security Gateway R81, R80, R77, R75, R71, R70
Who is Vulnerable?
Vulnerability Description	DCE/RPC stands for "Distributed Computing Environment / Remote Procedure Calls". It is a Remote Procedure Call system that allows software to work across multiple computers, as if it were all working on the same computer. This system allows programmers to write distributed software without having to worry about the underlying network code. There are many known vulnerabilities in applications based on the DCE-RPC protocol. Though IDS and IPS devices have signatures to detect attacks exploiting these vulnerabilities, these devices can be evaded by using big endian notation. The DCE-RPC FLAGS field contains a bit that specifies the endianity of the data that follows. Attackers may use big endian notation as an IDS/IPS evasion technique.

Protection Overview

This protection will detect and block all DCE-RPC traffic in big endian notation.

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

In the IPS tab, click Protections and find the DCE-RPC Big Endian 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: MS-RPC Enforcement Violation.
Attack Information: DCE-RPC Big Endian evasion technique