Security continues to be a balance between providing users with features and mitigating risk. . Client-side vulnerabilities seem to be the hole that many of us are stuck spinning our wheels in.
Even if you are patched...
There are still users who will be tricked, or will open any attachment just out of sheer curiosity. Let’s face it, it is likely part of their job to open documents (my favorite example is HR personnel, forced to open resumes in PDF and Word formats). Being up-to-date on the latest software is important, however VBScript macros embedded inside of Office documents can often lead to code execution just as easily as a software vulnerability. This month's patch update from Microsoft fixes seven vulnerabilities in Microsoft Office, but we shouldn't get hung up on the vulnerabilities themselves. We need to prevent the attacks from happening in the first place.
Getting to the bottom of the problem
Organizations need to look beyond patches and software security and define the real problem: users are receiving documents that allow code execution. Whether this stems from a software vulnerability or an embedded macro, the result is the same and attackers are bypassing the security mechanisms put in place. There are a few different ways to prevent this attack vector and a combination of the following approaches will likely be the most effective:
- Manage the configuration of the client, hardening the operating system and applications
- Read emails in plain text
- Disallow certain attachment types
- Scan documents with antivirus software both on the gateways and on the client system
- Disable features such as Office document macros
- Implement a security awareness program for end users
All of these measures go a long way to frustrate attackers. While you may never be able to stop a determined attacker 100% of the time, you can make the attacker's life more difficult. Another defensive measure that shows great promise is tracking where processes are connecting. For example, why should a Microsoft Word program be making an outbound TCP connection to the Internet? This behavior is anomalous and needs to be monitored and flagged as suspicious (or even blocked) by the operating system.
To further aid in your efforts to evaluate the dangers of the Microsoft Patch Tuesday mayhem, Tenable's Research team has published plugins for each of the security bulletins issued this month:
- MS10-087 - Nessus Plugin ID 50531 (Credentialed Check) - Fixes five vulnerabilities in Microsoft Office on both Windows and Mac OS X versions. This includes a buffer overflow vulnerability when processing RTF documents.
- MS10-088 - Nessus Plugin ID 50529 (Credentialed Check) - Fixes two vulnerabilities in Microsoft PowerPoint included with Windows Office XP, Windows Office 2003, and 2004 for Mac. In order to exploit either vulnerability, the user must open the PowerPoint file.
- MS10-089 - Nessus Plugin ID 50530 (Credentialed Check) - Four vulnerabilities in Forefront Unified Access Gateway are fixed in this bulletin, including a URL redirection flaw that allows attackers to redirect users to malicious web sites.
- Microsoft Security Bulletin Summary for November 2010
- OSVDB Microsoft Bulletins - Complete Reference
- Microsoft Patch Tuesday Roundup - October 2010 - "Nightmare" Edition
- Microsoft Patch Tuesday Roundup - September 2010 - "Silent but deadly" Edition
- Microsoft Patch Tuesday Roundup - August 2010 - "Geronimo!" Edition
- Microsoft Patch Tuesday Roundup - July 2010 - "Jedi Mind Trick" Edition
- Microsoft Patch Tuesday Roundup- June 2010 - "Everything is Vulnerable" Edition
- Microsoft Patch Tuesday Roundup- May 2010 - "Language Barrier" Edition
- Microsoft Patch Tuesday Roundup- April 2010 - "Superman" Edition
- Microsoft Patch Tuesday Roundup- March 2010 - "It Won't Happen To Me" Edition
- Microsoft Patch Tuesday Roundup- February 2010 - "From Microsoft with Love" Edition
- Microsoft Patch Tuesday Roundup- January 2010 - "Aged Cheese" Edition