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Flame Burns a Little Brighter

Posted June 4, 2012    BeyondTrust Research Team

Did you know that Microsoft’s Terminal Server Licensing Service (we’ll call it TSLS for convenience) generated certificates that could be used to sign code? No? Neither did Redmond. Flame leveraged a “0day” (zero day) within TSLS to sign its own code, allowing it to appear as if the code came from Microsoft. This allowed Flame to propagate itself in a network by fooling other machines into believing it was serving Windows Update packages, when in actuality, it was serving up Microsoft signed versions of Flame. More details follow… but first, here is some actionable intelligence:

What does this mean for you and your organization? Apply this fix (Bulletin, Patch) immediately. Unless the patch is applied, your machines may end up trusting malicious code. Retina provides detection for the vulnerable certificates via audit 16497 – Microsoft Revocation of Fraudulent Certificates (2718704).

What does this mean for Flame? It is the first confirmed 0day used by Flame. Albeit, this 0day does not grant an attacker the ability to remotely control a machine with the use of a malformed packet or PDF. However, the use of this vulnerability shows sophistication and access to undisclosed exploitable bugs that may hint at the overall cleverness of Flame. Flame has moved beyond the realm of exploiting known flaws, to the fertile lands of 0day.

So how did this all go down? Well that is a very interesting, yet brief, tale. It all starts with an infected machine on a network. We’ll call that infected box… “Machine A”. Machine A is infected and is looking for opportunities to infect other machines on its network. It sets up a server by the name of “MSHOME-F3BE293C” and starts listening to WPAD requests sent by machines set to automatically configure its proxy settings (Internet Properties –>Connections –>LAN Settings–>Automatically detect settings).

By listening and replying to WPAD requests, the infected machine can point other machines to its proxy configuration file (PAC); effectively, an attacker can then dictate that traffic pass through the infected machine. Once it falsely declares itself as the proxy for the domain, other unwitting (and currently uninfected) machines start routing traffic through Machine A. When Machine A eventually sees some Windows Update queries come across its desk, it replies with a fake update that proceeds to download Flame and *BLAM*, the infection spreads.

By leveraging WPAD weaknesses (which are no stranger to WPAD, see http://technet.microsoft.com/en-us/security/advisory/945713) and Microsoft signed executables, Flame was able to redirect traffic and then subsequently push malicious code onto target machines without any warnings or prompts, because MS code is to be trusted implicitly… Flame may potentially be more sophisticated and refined than its massive size may lead some to believe. Granted, Flame is still being analyzed, and from all estimates there is a long way to go, so stay tuned.

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Additional articles

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A Quick Look at MS14-068

Posted November 20, 2014    BeyondTrust Research Team

Microsoft recently released an out of band patch for Kerberos.  Taking a look at the Microsoft security bulletin, it seems like there is some kind of issue with Kerberos signatures related to tickets. Further information is available in the Microsoft SRD Blogpost So it looks like there is an issue with PAC signatures.  But what…

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Password Game Show

Managing Shared Accounts for Privileged Users: 5 Best Practices for Achieving Control and Accountability

Posted November 20, 2014    Scott Lang

How do organizations ensure accountability of shared privileged accounts to meet compliance and security requirements without impacting administrator productivity? Consider these five best practices…

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Triggering MS14-066

Triggering MS14-066

Posted November 17, 2014    BeyondTrust Research Team

Microsoft addressed CVE-2014-6321 this Patch Tuesday, which has been hyped as the next Heartbleed.  This vulnerability (actually at least 2 vulnerabilities) promises remote code execution in applications that use the SChannel Security Service Provider, such as Microsoft Internet Information Services (IIS). The details have been scarce.  Lets fix that. Looking at the bindiff of schannel.dll, we see a…

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