In 2015, Microsoft acknowledged 571 vulnerabilities1 across their entire solution suite. 91, or 16%, of these vulnerabilities allowed for the attacker to elevate privileges based on the exploit. These are the worst vulnerabilities to consider in any environment outside of ones that are remotely exploitable with no user interaction.
Interestingly, the remaining 84% of acknowledged Microsoft vulnerabilities did not contain any attack vectors which allowed for the exploit to gain privileges. If the exploit executed a standard user, or with a least privilege model, the executed code and the payload would be confined to whatever the standard user could perform. (Normal restrictions include not modifying the systems processes or services, registry, key system files, or even installing software.)
The numbers don’t lie: Reducing privileges, and therefore restricting exploit and payload access to modify an asset, helps to mitigate the risks from known vulnerabilities.
Historical data supports this fact: Least privilege works in mitigating risks in Microsoft environments
Let’s dive a little deeper to validate our assumption here. From 1999 to the end of 2015, Microsoft publicly documented 4,175 vulnerabilities. 461 of them (11%) allowed for the elevation of privileges, while 89% of vulnerabilities did not contain any attack vectors to raise privileges since we started keeping track of CVE's.
Based on this history, reducing privileges has proven to be an effective method to limit un-patched risks for all Microsoft solutions over time. It is important to note this not a perfect solution, rather it is a containment model and is as effective as the stringency of privileges granted and vulnerabilities present on the system. Any form of excessive privilege could be leveraged by the exploit if it was designed to do so. Thus, keeping the model strict is fundamentally key.
Extending least privilege to applications
Couple vulnerability management and least privilege together, and allow the data to be shared in real time, so you can effectively measure an application or operating system’s risk as it is being used and modify the privileges accordingly. This will enable you to never give administrator rights to an application with known vulnerabilities or even deny the execution on those 11% of high risk threats.
In other words, 84% percent of Microsoft vulnerabilities cannot change privileges. For the other 16%, if the risk is known, why would you ever give that un-patched component or third party application excessive rights until it is patched? This ensures that even the simplest of exploits are always contained even if rights are needed to execute them.
For more on how BeyondTrust can help you mitigate the risks of vulnerabilities, and simplify the enforcement of least privilege across your Windows environment, contact us today.
1 CVEDetails.com
