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Security Best Practice: Blocking Null Prefix in DNS MX Records

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Check Point Reference: SBP-2010-16
Date Published:
Severity:
Last Updated:
Source: Microsoft Security Bulletin MS10-024
Industry Reference(s): CVE-2010-0024
Protection Provided by: Security Gateway
  • R70
VPN-1
  • NGX R65
VSX
  • NGX R65
InterSpect
  • NGX
IPS-1
  • IPS-1
  • IPS-1 NGX R65
Who is Vulnerable?
Microsoft Windows 2000 SP4
Windows XP SP2
Windows XP SP3
Windows XP Professional x64 Edition SP2
Windows Server 2003 SP2
Windows Server 2003 x64 Edition SP2
Windows Server 2003 with SP2 (Itanium)
Windows Server 2008 for 32-bit Systems
Windows Server 2008 for 32-bit Systems SP2
Windows Server 2008 for x64-based Systems
Windows Server 2008 for x64-based Systems SP2
Windows Server 2008 (Itanium) SP2
Windows Server 2008 R2 for x64-based Systems
Microsoft Exchange Server 2003 SP2
Vulnerability Description
A denial of service vulnerability has been reported in the way that Microsoft Windows Simple Mail Transfer Protocol (SMTP) component handles specially crafted DNS Mail Exchanger (MX) resource records. The mail exchange (MX) resource record specifies a mail exchange server for a DNS domain name. A remote attacker may trigger this vulnerability via a specially crafted DNS request with a null prefix in the MX record. Successful exploitation of this issue could cause the affected system to stop accepting requests.
Update/Patch Available
Apply patches:
Microsoft Security Bulletin MS10-024
Vulnerability Details
The vulnerability is due to an error in the Microsoft Windows SMTP component that incorrectly parses specially crafted DNS Mail Exchanger (MX) records. A remote attacker may exploit this flaw by sending a specially crafted network message to a computer running the SMTP service. Successful exploitation of this issue will create a denial of service condition, causing the SMTP service to stop responding until restarted.

Protection Overview
This protection detects and blocks null prefix of DNS MX records.

In order for the protection to be activated, update your Security Gateway/VPN-1 product to the latest IPS/SmartDefense update. For information on how to update IPS/SmartDefense, go to SBP-2006-05, Protection tab and select the version of your choice. 

To configure the defense, select your product from the list below and follow the related protection steps.

Security Gateway R70

How Can I Protect My Network?
1. In the IPS tab, click Protections > By Protocol > Application Intelligence > DNS > Malformed Resource Records.
2. In the right pane, double-click the DNS MX Record Null Prefix protection.
3. In the Protection Details window, click on Edit. Choose the protection's Action (Override IPS Policy with: Prevent/Detect), and apply Additional Settings.
4. Install policy on all modules.

How Do I Know if My Network is Under Attack?
SmartView Tracker will log the following entries:

Attack Name: DNS Enforcement Violation
Attack Information: DNS MX record null prefix

VPN-1 NGX R65 & VPN-1 VSX NGX R65

How Can I Protect My Network?
1. In the SmartDefense tab, click Application Intelligence > DNS > Malformed Resource Records.
2. Select the following protection:

DNS MX Record Null Prefix

3. In the configuration pane, under Settings > Mode, check Active.
4. Install policy on all modules.

How Do I Know if My Network is Under Attack?
SmartView Tracker will log the following entries:

Attack Name: DNS Enforcement Violation
Attack Information: DNS MX record null prefix

InterSpect NGX

How Can I Protect My Network?
1. In the left pane, select Profiles > Default Protection and select the SmartDefense page of the profile.
2. In the SmartDefense tree, click Application Intelligence > DNS > Malformed Resource Records.
3. Select the following protection:

DNS MX Record Null Prefix

4. Install security policy on all modules.

How Do I Know if My Network is Under Attack?
SmartView Tracker will log the following entries:

Attack Name: DNS Enforcement Violation
Attack Information: DNS MX record null prefix

IPS-1 & IPS-1 NGX R65

How Can I Protect My Network?
1. In the IPS-1 Policy Manager, click on the Protection tab.
2. In the Protection tree, click Network Security > DNS, and select the Labels protection group.
3. Click Binary Data in DNS Label (IPS-1 NGX R65 only).
4. In the configuration pane, under Settings, check Active.
5. Click on Install Policy.

How Do I Know if My Network is Under Attack?
Upon attack, the following entries will be logged:

Alert Name: DNS Names and Labels Alerts
Description: Binary Data in DNS Label