Check Point Advisories

Invalid Bind NAK Messages

Vulnerability
Protection

Check Point Reference:	CPAI-2007-0139
Date Published:	6 Sep 2007
Severity:	Medium
Last Updated:	Thursday 06 September, 2007
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 an invalid value in the NDR field. Attackers may use this as an IDS/IPS evasion technique.

Protection Overview

The DCE-RPC client sends the DCE-RPC server a Bind request and may receive a Bind Nak response. If a Bind Nak response is not preceded by a Bind request this protection blocks the response.

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 Invalid Bind NAK Messages 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: Blocked out of state MS-RPC Bind Nak message