Update: 8th November:
The Microsoft zero day vulnerability discussed in this post has now been patched. Please refer to this post for the appropriate information and download links.
Earlier this week Google publicly disclosed (defined) details of a new zero day (defined) vulnerability affecting supported versions of Windows up to Windows 10. Fortunately, the disclosure only included minimal details.
Why Should These Issues Be Considered Important?
The vulnerability disclosed by Google could result with an attacker being able to elevate their privileges (defined) on an affected system. However, when used in combination with a previously patched Adobe Flash Player vulnerability (reference previous post) this could result in a Windows system under your responsibility or in your ownership to have a backdoor (defined) installed.
Some good news is that this new exploit primarily targets organisations that operate in the following sectors (thus all other organisations are at somewhat reduced risk): government, intelligence or military organisations.
The nature of the backdoor is the decision of the attacker but would usually include a means of remaining persistent on the system and allowing the attacker to remote access the infected system. This backdoor can then be used to move data of the attacker’s choice off the affected system. The APT group known as STRONTIUM by Microsoft (other aliases used in the wider cyber security industry are APT28, also aka Sofacy aka Fancy Bear aka TsarTeam aka Sednit aka PawnStorm). STRONTIUM is also known for moving laterally throughout the network which they compromise (where the pass the hash (PtH) (defined) technique is the method of choice to do so).
How Can I Protect Myself From This Issue?
While a patch from Microsoft is in progress (scheduled for release on the 8th of November): follow safe email guidelines namely don’t click on unexpected/unsolicited links or open potentially dangerous email attachments to prevent the execution (carrying out of) the exploits actions in the first instance.
If you use the Microsoft Edge or Google Chrome web browsers the exploit for the local elevation of privilege vulnerability will be mitigated. This is due to Chrome’s sandbox (defined) blocking the use of API (defined) calls to the win32k.sys driver (defined). This in addition to its existing mitigations when installed on Windows 10 which I previously discussed.
Microsoft Edge on the other hand implements Code Integrity to prevent the next steps of exploitation.
To protect endpoints within your organisation you could consider utilising the logging capabilities of Microsoft EMET and Systinternals’ Sysmon by processing their logs using a SIEM (defined) and taking action when that SIEM a alerts you to suspicion activity. This is especially true since this exploit can occur from within web browsers, the Java JRE, Microsoft Word and Microsoft PowerPoint (namely that these applications are used to open suspicious/untrusted files).
My thanks to a colleague (you know who you are!) for compiling very useful information for this blog post.