USING EMET TO DEFEND AGAINST TARGETED ATTACKS

PRESENTED BY ROBERT HENSING – SENIOR CONSULTANT – MICROSOFT CORPORATION

WHOAMI• Robert Hensing• 15 year Microsoft veteran• Developed original versions of W.O.L.F. and AutoDump+ (tools used by

Customer Support for Incident Response and Debugging respectively)• Trustworthy Computing Division alumni

• 5 year tour in MSRC Engineering – Defense team• Co-Developed GUT (swiss army knife hex editor / fuzzer / vulnerability detection

framework)• Co-Developed a technique that uses the Windows shim engine to mitigate vulnerable

code via ‘Shimpatches’ (as featured in recent IE Security Advisories)• Currently a boring C# Developer Consultant in National Security Group practice

• I used to be somebody.

TRUSTWORTHY COMPUTING - SECURITY CENTERS

Protecting Microsoft customers throughout the entire life cycle(in development, deployment and operations)

Microsoft Security

Engineering Center (MSEC)

Security Assurance

Security Science

SDL

Microsoft Malware Protection Center

(MMPC)ReleaseRelease

Product Life CycleProduct Life Cycle

Microsoft Security

Response Center(MSRC)Ecosystem

StrategyMSRC Ops

MSRC Engineering

ConceptionConception

Result: Attackers only have to find one vulnerability, and they get to use it for a really long time.

THE SOFTWARE VULNERABILITY ASYMMETRY PROBLEM

Defender must fix all vulnerabilities in all software – attacker wins by finding and exploiting just one vulnerability

Threats change over time – state-of-the-art in vulnerability finding and attack techniques changes over time

Patch deployment takes time – vendor must offset risks to stability & compatibility, customer waits for servicing cycle

EXPLOIT ECONOMICS

5

Gains per use

XOpportunities to use

Cost to acquire vulnerability

+Cost to weaponize

Attacker Return -=

Desired Result: Usable attacks will be rare and require significant engineering; working exploits will become scarce and valuable

EXPLOIT ECONOMICS

We can decrease Attacker Return if we are able to…Increase attacker investment required to find usable vulnerabilities• Remove entire classes of vulnerabilities where possible• Focus on automation to scale human efforts

Increase attacker investment required to write reliable exploits• Build mitigations that add brittleness• Make exploits impossible to write completely reliably

Decrease attacker’s opportunity to recover their investment• Shrink window of vulnerability• Fewer opportunities via artificial diversity• Enable rapid detection & suppression of exploit usage

INCREASE ATTACKER INVESTMENT REQUIRED TO FIND VULNERABILITIES

Exploit Economics Strategy – Step 1

7

EMBEDDING SECURITY INTO SOFTWARE AND CULTURE

Tactics for Vulnerability ReductionRemove entire classes of vulnerabilities • Security Tooling• Additional product features

Remove all currently findable vulnerabilities• Complete automation of tooling

• SDL tools, Threat Modeling tool• Fuzzing toolsets + ways to streamline & improve triage• Tool overlays to increase signal-to-noise and focus attention on the right code

• Verification & enforcement• Audit individual tool usage via process tools• Process tools required for SDL signoff - policy enforcement

Ongoing Process Improvements

PREVENT RELIABLE EXPLOITATION OF VULNERABILITIES

Exploit Economics Strategy – Step 2

EMBEDDING SECURITY INTO SOFTWARE AND CULTURE

Tactics to Frustrate ExploitsReduce the surface we have to defend• Attack surface reduction• Design additional product mitigations

Make remaining vulnerabilities difficult or impossible to exploit• Build mitigations that add exploit brittleness

Ongoing Process Improvements

DIGITAL COUNTERMEASURES

• Improve system survivability against exploitation of unknown vulnerabilities•Three goals:• Increase attacker requirements – e.g. must be

authenticated, local subnet only• Deterrent – no economically reliable exploit

exists•Mitigation – Break 100% reliable universal

exploits•Often must be combined together•Even when successful, the result is still impactful to the user 11

MITIGATION APPROACHES

• Utilize secrets such that guessing impairs exploit reliability• /GS: Protect stack buffers by checking random cookies

placed between them and control structures• Function Pointer Encoding

12

Utilize Knowledge Deficits

Artificial Diversity

Enforce Invariants

ASLR: Address Space Layout Randomization

Data Execute Protection (DEP)Heap & pool metadata checks SafeSEH / SEH Overwrite Protection (SEHOP)

MEMORY SAFETY MITIGATIONS ROADMAP

13

Stack

Heap / Pool

Executable Code

/GS 1.0 /GS 1.1

Heap 1.0

DEP ASLR DEP IE8

20072006200520042003

/GS 2.0

2008

/NXCOMPAT

Heap 2.0

HeapTerm

EH4 SEHOP /GS 3.0

DEP+ATL

Safe Unlinking

2009

DEP O14

2010 2011

SEHOPIE9

2013

SEHOP + HEASLR +ForceASLR IE10

Heap Rand / Hardening

2012

• Mitigations in software have evolved significantly since the release of Windows XP• Internet Explorer 10 on Windows

8 benefits from an extensive number of platform security improvements (not available to Internet Explorer 8 on Windows XP)

SOFTWARE SECURITY HAS EVOLVEDSEHOPProtected Mode Enhanced Protected Mode (EPM)Virtual Table GuardASLR Stack randomization Heap randomization Image randomization Force image randomization Bottom-up randomization Top-down randomization High entropy randomization PEB/TEB randomizationHeap hardening Header encoding Terminate on corruption Guard Pages Allocation randomization Safe unlinking Header checksums/GS Enhanced/GSSafeSEH

NoNoNoNoLimitedNoNoNoNoNoNoNoNoLimitedNoNoNoNoYesYesYesNoYes

YesYesYesYesExtensiveYesYesYesYesYesYesYesYesExtensiveYesYesYesYesYesYesYesYesYes

Windows XP SP3 Internet Explorer 8

Windows 8Internet Explorer 10

ENHANCED MITIGATION EXPERIENCE TOOLKIT (EMET) Offers security mitigations for most software

Old applications Third party software Line of business applications

Brings newer security mitigations to older platforms

Provides exclusive state of the art security mitigations to block current exploit techniques

Download the latest bits:http://www.microsoft.com/emet EMET 4.1 supported on Windows XP EMET 5.0 and later require Vista or higher

EVOLUTION OF EMET MITIGATIONS & FEATURESMitigations in v1.0• Dynamic DEP• SEHOP• NULL Page protection

Mitigations in v2.0• Mandatory ASLR• EAT Access Filtering• Heap Spray Allocation

Features added in v3.0• 3 Protection Profiles• ADMX Files for Group

Policy Management• EMET Notifier (alerts

user when mitigations were enforced)

Mitigations in v3.5• Anti-ROP mitigations:

• Caller Checks• Exec Flow Simulation

• Stack Pivot Mitigation• Load Library Checks• Memory Protection Checks

EVOLUTION OF EMET MITIATIONS (CONTINUED)Mitigations & Features in v4.0• Certificate Pinning• Early Warning Program

(telemetry via Microsoft Error Reporting)• Could be used to find

733t 0-day!• Blocks known bypasses

(deep hooks)• Updated rules to fix app-

compat issues• Audit Mode (i.e. No Kill

Mode)• Configuration Wizard

Mitigations & Features in v4.1• Updates to default

protection profiles• Improved Event Logging• App-Compat updates / fixes• Fix to allow shared remote

desktopsMitigations & Features in v5.0 (Vista+)• Attack Surface Reduction

• Preventing unwanted 3rd party modules from loading in applications

• EAF+• Adds KernelBase to

protected functions• Adds additional checks to

existing protected exports

MS13-008 – INTERNET EXPLORER CVE-2012-4792 (CBUTTON USE AFTER FREE)• 0-day vulnerability being used in limited targeted

attacks prior to bulletin release discovered by FireEye circa 12/27/2012

• Vulnerability about as bad as it gets!• Remote Code Exec vulnerability in all versions of IE

(at the time) and exploitable via a web page• Fixed by MS13-008 on 1/14/2013

http://technet.microsoft.com/en-us/security/bulletin/ms13-008 • Standard mitigations in the bulletin were• Don’t open Office documents• Set Internet zone to High (yeah right)• Disable Active Scripting and ActiveX controls

(yeah right)

DEMONSTRATION - EMET VS. MS13-008CVE-2012-4792 (CBUTTON UAF)

A ‘watering hole’ attack from www.issa-balt.org

DEMONSTRATION

RECENT EMET RELATED DEVELOPMENTS• ATTACKERS VS. EMET IN THE NEWS• February 11th

• SECURITY COMPANY VS. EMET IN THE NEWS• February 24th

• MICROSOFT VS. EMET IN THE NEWS• February 25th

THIS EXPLOIT ATTEMPT WILL SELF-DESTRUCT . . .

THIS AIN’T A SCENE IT’S A @#$% ARMS RACE• On February 24th Bromium Labs claimed to be able to

bypass all EMET 4.1 mitigations leading to a big press cycle during the RSA conference

• They discussed ways of bypassing the various ROP mitigations individually, and a way of bypassing the StackPivot mitigation.

• They created an exploit payload that made use of many of their discoveries but that eventually needed to call NtProtectVirtualMemory (an API that is only protected when ‘Deep Hooks’ is enabled)• They noted Deep Hooks was not enabled by default so this was

convenient for them.• So EMET 5.0 will enable Deep Hooks by default!

• This required working with some vendors (McAfee HIPS) to wait for updated versions of their products to be released.

• Bottom Line – EMET is not invincible but it does raise the bar for adversaries and Microsoft is committed to investigating new bypasses and addressing them in future versions of EMET if possible.

OH NOZ!!! THE END IS NEAR! (0-DAY MAY)• On April 8, 2014, Windows XP will no longer be

supported by Microsoft. This means customers will no longer receive:

New security updatesNon-security hotfixesFree or paid assisted support options Online technical content updates

• New vulnerabilities discovered after support ends for Windows XP will not be addressed without an expensive custom support agreement

• If only there was something inexpensive that you could do to protect all those un-patched Windows XP boxes from exploit attempts.

CALL TO ACTION• Follow the Security Research and Defense blog to stay on stop of the latest

trends in security research and defense!• http://blogs.technet.com/b/srd/

• Keep an eye on www.microsoft.com/emet for updates and announcements• Evaluate and Deploy EMET 4.1 (XP+) now or EMET 5.0 (Vista+) when it releases.• Protect critical applications such as Internet Explorer, Firefox, Office, Adobe

Acrobat etc• Monitor for EMET related events in the event log using System Center or other

Enterprise monitoring software to spot 733t 0-day attempts (that don’t detect EMET and self-destruct! )• Support: http://

social.technet.microsoft.com/Forums/security/en-US/home?forum=emet