Context:
As some of you have no doubt seen, there is a new 0 Day vulnerability in IE6 – IE11 that allows one to bypass some of Window’s primary security mechanisms of ASLR & DEP. Specifically, the way IE (mis)handles Adobe Flash allowed this issue to happen. There currently is no patch from Microsoft, but I do expect one within the next couple days.
The initial exploitation of this vulnerability was targeted to IE9 – IE11 and a specific set of users that an APT group was targeting, but we are now seeing more generalized/non-targeted attacks.
There are a few reasons that this is a significant vulnerability, other than the fact that it is a 0 Day…
-According to Microsoft’s current policy of end of life applications, this vulnerability will not be patched on Windows XP—This means that no matter what version of IE you are running on XP (IE6 – IE8), it will always be vulnerable to this exploit unless extra action is taken (see mitigation options below)
-This vulnerability affects such a wide set of IE versions—In 2013, these versions of IE made up 53% of the desktop browser market share [src]
General Mitigation Options:
The following are the top 5 ways to mitigate this exploit—
–Disable/Remove Adobe Flash: Because this vulnerability is really a vulnerability between Flash & IE, disabling or removing Flash will remove the vulnerability.
–Enable IE’s “Enhanced Protected Mode” : EPM was introduced in IE10 as an enhancement to previous versions of IE’s “Protected Mode.” EPM can have some unintended compatibility issues with other applications/web-apps, so make sure to test before rolling out.
–Use the Enhanced Mitigation Experience Toolkit: [SRC] I have discussed EMET quite a bit in the last year, but if you are not aware of what it is, Brian Krebs has a good primer on it. [SRC]
–Use a different browser: Because this is a vulnerability in IE’s handling of corrupted flash files, switching to a different browser will mitigate the issue—keep in mind that other installed apps (Microsoft Office, etc) may use the IE engine to render HTML and Flash files, which would bring the particular computer back into the scope of this vulnerability.
-Josh
Defensive Depth 