Maliciously crafted files can disable Microsoft's antimalware products

A vulnerability in the engine used by many Microsoft antimalware products can lead to a persistent denial-of-service condition

A vulnerability allows attackers to disable Microsoft's antimalware products by sending specifically crafted files to users via websites, email or instant messaging applications.

The vulnerability is located in the Microsoft Malware Protection Engine, which sits at the core of many Microsoft security products for desktops and servers including Microsoft Forefront Client Security, Microsoft System Center 2012 Endpoint Protection, the Microsoft Malicious Software Removal Tool, Microsoft Security Essentials, Windows Intune Endpoint Protection and Windows Defender, which comes pre-installed in Windows Vista and later.

Microsoft fixed the vulnerability in Microsoft Malware Protection Engine 1.1.10701.0 released Tuesday. For home users, the new version should typically download and install automatically within 48 hours, but administrators in enterprise environments should make sure that their update management software is configured to approve the engine updates.

If left unpatched, the vulnerability can be exploited to force the Microsoft Malware Protection Engine into a scan timeout, essentially leading to a denial-of-service vulnerability. When this happens, the antimalware product will stop monitoring the system for threats until the rogue file is removed and the malware protection service is restarted.

"There are many ways that an attacker could place a specially crafted file in a location that is scanned by the Microsoft Malware Protection Engine," Microsoft said in a security advisory published Tuesday. "For example, an attacker could use a website to deliver a specially crafted file to the victim's system that is scanned when the website is viewed by the user. An attacker could also deliver a specially crafted file via an email message or in an Instant Messenger message that is scanned when the file is opened."

In addition, if the Malware Protection Engine runs on a Windows server hosting a website that accepts user-supplied content, an attacker could exploit the vulnerability by uploading a specially crafted file through the website.

Microsoft credited Tavis Ormandy, an information security engineer at Google, with discovering and reporting the vulnerability to the company.

Ormandy has found vulnerabilities in antimalware software in the past. In 2012 he found critical vulnerabilities in Sophos Antivirus.

Specific details about how to create the rogue files that prevent the Microsoft Malware Protection Engine from functioning properly were not released, but Ormandy hinted on Twitter that the problem involves JavaScript.

"This was an interesting bug in the JavaScript interpreter in Windows Defender," he said. "Yes, it has a JS interpreter."

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags Microsoftpatch managementmalwareGooglesophosantiviruspatchesExploits / vulnerabilitiesDesktop security

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.
Lucian Constantin

Lucian Constantin

IDG News Service
Show Comments

Cool Tech

Bang and Olufsen Beosound Stage - Dolby Atmos Soundbar

Learn more >

Toys for Boys

Nakamichi Delta 100 3-Way Hi Fi Speaker System

Learn more >

ASUS ROG, ACRONYM partner for Special Edition Zephyrus G14

Learn more >

Sony WF-1000XM3 Wireless Noise Cancelling Headphones

Learn more >

Family Friendly

Philips Sonicare Diamond Clean 9000 Toothbrush

Learn more >

Mario Kart Live: Home Circuit for Nintendo Switch

Learn more >

Stocking Stuffer

SunnyBunny Snowflakes 20 LED Solar Powered Fairy String

Learn more >

Teac 7 inch Swivel Screen Portable DVD Player

Learn more >

Christmas Gift Guide

Click for more ›

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Tom Pope

Dynabook Portégé X30L-G

Ultimately this laptop has achieved everything I would hope for in a laptop for work, while fitting that into a form factor and weight that is remarkable.

Tom Sellers

MSI P65

This smart laptop was enjoyable to use and great to work on – creating content was super simple.

Lolita Wang

MSI GT76

It really doesn’t get more “gaming laptop” than this.

Jack Jeffries

MSI GS75

As the Maserati or BMW of laptops, it would fit perfectly in the hands of a professional needing firepower under the hood, sophistication and class on the surface, and gaming prowess (sports mode if you will) in between.

Taylor Carr

MSI PS63

The MSI PS63 is an amazing laptop and I would definitely consider buying one in the future.

Christopher Low

Brother RJ-4230B

This small mobile printer is exactly what I need for invoicing and other jobs such as sending fellow tradesman details or step-by-step instructions that I can easily print off from my phone or the Web.

Featured Content

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?