Microsoft updates EMET security tool to fix compatibility issues, harden exploit mitigations

EMET 5.1 fixes incompatibilities detected between certain mitigations and popular software programs

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Microsoft's Enhanced Mitigation Experience Toolkit (EMET), a security program popular with companies, was updated Monday to harden the exploit mitigations that it adds to other programs and to address compatibility issues with some of them.

The compatibility issues affected popular applications including Internet Explorer, Adobe Reader, Adobe Flash, and Mozilla Firefox when EMET mitigations like Export Address Table Filtering Plus (EAF+) were applied to them.

Like most EMET mitigations, EAF+ is a set of safeguards and checks designed to block the execution of arbitrary code when memory corruption vulnerabilities are exploited. It was first added in EMET 5.0, released in July.

In addition to addressing the compatibility issues, EMET 5.1 also improves and hardens existing mitigations "to make them more resilient to attacks and bypasses," the EMET team said in a blog post Monday.

It's particularly important for users of Internet Explorer 11 on Windows 7 or Windows 8.1 to install the new version because the browser security patches scheduled to be released today are known to cause compatibility issues with EAF+.

EMET 5.1 also adds a new "local telemetry" feature that allows users to save memory dumps whenever an EMET mitigation is triggered. These memory dumps can later be analyzed to determine what triggered the mitigations, whether it was a malicious exploit or something else.

EMET is popular within enterprises environments because it allows companies to protect their end-point systems from software exploits even before the targeted vulnerabilities are patched. The tool can enforce memory protections like Data Execution Prevention (DEP), Address Space Layout Randomization (ASLR) and 12 others on running programs that lack them by default.

It can also enforce pre-defined SSL certificate pinning rules in Internet Explorer. These rules can prevent man-in-the-middle attacks that use digital certificates for popular websites that are technically valid, but were illegally obtained -- for example, by compromising a certificate authority.

A complete list of changes and improvements in EMET 5.1 is available in a Microsoft knowledge base article.

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