Close
  • Latest News
  • Big Data and Analytics
  • Cloud
  • Networking
  • Cybersecurity
  • Applications
  • IT Management
  • Storage
  • Sponsored
  • Mobile
  • Small Business
  • Development
  • Database
  • Servers
  • Android
  • Apple
  • Innovation
  • Blogs
  • PC Hardware
  • Reviews
  • Search Engines
  • Virtualization
Read Down
Sign in
Close
Welcome!Log into your account
Forgot your password?
Read Down
Password recovery
Recover your password
Close
Search
Logo
Logo
  • Latest News
  • Big Data and Analytics
  • Cloud
  • Networking
  • Cybersecurity
  • Applications
  • IT Management
  • Storage
  • Sponsored
  • Mobile
  • Small Business
  • Development
  • Database
  • Servers
  • Android
  • Apple
  • Innovation
  • Blogs
  • PC Hardware
  • Reviews
  • Search Engines
  • Virtualization
More
    Home Cybersecurity
    • Cybersecurity

    Malware Abuses Windows EFS to Thwart Security Analysis

    By
    Brian Prince
    -
    June 12, 2013
    Share
    Facebook
    Twitter
    Linkedin

      Getting inside a network is only part of the fight for attackers; the other is avoiding detection for as long as possible. Yet another part is keeping analysts from dissecting and reverse-engineering their malicious wares once they end up in the hands of their opponents.

      Recently, researchers at Symantec found a backdoor, known as Tranwos, abusing a Windows feature, known as the Encrypting File System (EFS), to make the lives of security researchers more difficult.

      “Not only is it trivial for program code to use EFS, it’s also very effective at preventing forensic analysis from accessing the contents of the file,” blogged Symantec security researcher Kazumasa Itabashi.

      The malware creates a folder and then calls the EncryptFileW API in order to encrypt it, making it so all files and folders subsequently created in the encrypted folder will be encrypted automatically by Windows, the researcher explained. The malware also copies itself as the file name wow.dll in the folder and modifies the Characteristic attribute of the PE header in order to change to a DLL file.

      “In some cases, security researchers may use another operating system, such as a version of Linux bootable from a removable drive, in order to retrieve malicious files from a compromised computer,” Itabashi blogged. “This method is useful when retrieving files from a computer compromised by a rootkit. However, it’s impossible to get the file wow.dll by this method because the DLL file is encrypted on the EFS.”

      “A user account that executes this threat can see the contents of the file and change the status of the encryption,” he continued. “As this threat makes it impossible for researchers to use forensic tools, as we normally would, we have to manually execute the threat on a test computer to gather the contents of the file. The purpose of this threat using EFS is only to prevent forensic analysis from retrieving the contents of itself.”

      It is not unusual for malware to take steps to thwart analysts.

      “One of the techniques that isn’t necessarily newer, but will always make life difficult is malicious activity within memory with minimal interaction with the file system,” said Will Irace, vice president of threat research at General Dynamics Fidelis Cybersecurity Solutions. “When a piece of malware is found on a system, artifacts about the malware and what files the malware created can normally be found.”

      Some malware, he explained, installs itself as a service, some gains persistence through auto-runs and some produce obfuscated logs.

      “When this happens, it is a simple task of finding out what the malware changes and creates on the system to determine if a system is compromised,” Irace said. “It becomes more complicated if the malware operates solely out of memory. It is difficult to determine the malware operations when the malicious software runs out of memory because memory is volatile, and if not saved shortly after operation, the activity can be lost.”

      “Another notable technique found in some malware has been modular design,” he continued. “By this we mean that the malicious software is created in a way that allows for the actors to dynamically load and unload functions to the malware –i.e., [the] threat actor sends new functionality from the [command and control] server to allow the malware to start performing keystroke logging. This allows the actors to change the ability of the malware on the fly, and makes research and defense from the malware tricky.”

      Traditional signatures or heuristics won’t always catch this type of malware because of the behavior changes based on the module that is added, he said.

      Such evasion techniques are part of the evolution of malware, noted Satnam Narang, security response manager at Symantec.

      “Essentially, we will see malware use certain evasion techniques, those techniques are discovered, and the malware authors in turn change their routine or develop new techniques,” said Narang. “This is a pattern that gets repeated pretty much across the board.”

      Brian Prince

      MOST POPULAR ARTICLES

      Cybersecurity

      Visa’s Michael Jabbara on Cybersecurity and Digital...

      James Maguire - May 17, 2022 0
      I spoke with Michael Jabbara, VP and Global Head of Fraud Services at Visa, about the cybersecurity technology used to ensure the safe transfer...
      Read more
      Cloud

      Yotascale CEO Asim Razzaq on Controlling Multicloud...

      James Maguire - May 5, 2022 0
      Asim Razzaq, CEO of Yotascale, provides guidance on understanding—and containing—the complex cost structure of multicloud computing. Among the topics we covered:  As you survey the...
      Read more
      Big Data and Analytics

      GoodData CEO Roman Stanek on Business Intelligence...

      James Maguire - May 4, 2022 0
      I spoke with Roman Stanek, CEO of GoodData, about business intelligence, data as a service, and the frustration that many executives have with data...
      Read more
      IT Management

      Intuit’s Nhung Ho on AI for the...

      James Maguire - May 13, 2022 0
      I spoke with Nhung Ho, Vice President of AI at Intuit, about adoption of AI in the small and medium-sized business market, and how...
      Read more
      Applications

      Cisco’s Thimaya Subaiya on Customer Experience in...

      James Maguire - May 10, 2022 0
      I spoke with Thimaya Subaiya, SVP and GM of Global Customer Experience at Cisco, about the factors that create good customer experience – and...
      Read more
      Logo

      eWeek has the latest technology news and analysis, buying guides, and product reviews for IT professionals and technology buyers. The site’s focus is on innovative solutions and covering in-depth technical content. eWeek stays on the cutting edge of technology news and IT trends through interviews and expert analysis. Gain insight from top innovators and thought leaders in the fields of IT, business, enterprise software, startups, and more.

      Facebook
      Linkedin
      RSS
      Twitter
      Youtube

      Advertisers

      Advertise with TechnologyAdvice on eWeek and our other IT-focused platforms.

      Advertise with Us

      Menu

      • About eWeek
      • Subscribe to our Newsletter
      • Latest News

      Our Brands

      • Privacy Policy
      • Terms
      • About
      • Contact
      • Advertise
      • Sitemap
      • California – Do Not Sell My Information

      Property of TechnologyAdvice.
      © 2021 TechnologyAdvice. All Rights Reserved

      Advertiser Disclosure: Some of the products that appear on this site are from companies from which TechnologyAdvice receives compensation. This compensation may impact how and where products appear on this site including, for example, the order in which they appear. TechnologyAdvice does not include all companies or all types of products available in the marketplace.

      ×