FileFix is an emerging attack technique that exploits the way Windows and web browsers manage the saving process of HTML web pages, effectively circumventing built-in Windows security measures. If executed successfully, this method can lead to severe security breaches, including ransomware deployment, credential theft, and the installation of various forms of malware. In this comprehensive guide, we will explore the key strategies to safeguard your computer against potential FileFix threats.
Understanding the Mechanics of a FileFix Attack
Uncovered by security expert mr.d0x, the FileFix attack manipulates the handling of local HTML application files and the Mark of the Web (MoTW) security feature in Windows. When users utilize the “Save as” option on a webpage, browsers typically fail to tag it with MoTW, which is intended to alert security systems like Windows Security to scan the file for malicious content.
Furthermore, when a file is saved with a.hta (HTML application file) extension, it can be executed immediately under the current user account without undergoing security checks. A malicious website can trick users into saving it as a.hta file, thereby allowing the inserted harmful code to run as soon as the file is opened, evading detection by Windows security systems.
While persuading users to save a malicious file is inherently challenging, tactics similar to those used by EDDIESTEALER can be employed. This includes social engineering methods that manipulate individuals into saving sensitive information, such as MFA codes, with misleading.hta extensions.
There are numerous preventive measures that can block this attack vector effectively. Below are several key strategies.
Steer Clear of Suspicious Web Pages
The initial step in the FileFix attack involves saving a malicious webpage; thus, avoiding such sites entirely prevents the attack. Always use up-to-date browsers like Chrome, Edge, or Firefox, which incorporate phishing detection and malware protection features. On Google Chrome, enabling Enhanced Protection can provide real-time AI-driven threat detection.
Many malicious sites are propagated through phishing emails masquerading as legitimate sources. Being able to identify these emails is crucial, and avoiding interaction with them can significantly reduce the risk of falling victim to various cyber threats. If you inadvertently land on a dubious site, there are effective ways to assess its legitimacy.
Visibility of File Extensions in Windows
In Windows 11, file extensions are hidden by default, leading users to overlook changes from.html to.hta. To combat this, it’s advisable to make file extensions visible, ensuring users can recognize the actual file type regardless of any deceptive naming.
To enable visibility of file extensions, follow these steps:
- Open File Explorer.
- Hit the See more button (three dots) and select Options.
- Navigate to the View tab and uncheck the box labeled Hide extensions for known file types.
With this change, file extensions will be displayed, even within the download window when saving a webpage.
Set Notepad as the Default Program for.hta Files
Mshta is the default application responsible for executing.hta files. By reassigning the.hta file association to Notepad, these files will open as text documents instead of running scripts, thus preventing execution of potentially harmful content.
This adjustment is unlikely to disrupt general users, as.hta scripts are primarily used by IT professionals or for specific enterprise applications. To implement this change, perform the following:
- Access Windows Settings and navigate to Apps -> Default Apps.
- In the search bar under Set a default for a file type or link type, type “.hta”.
Disabling Mshta to Prevent HTML Execution
An additional preventive method involves completely disabling the Mshta application to thwart all.hta script executions. This can be accomplished by renaming the “mshta.exe” file to “mshta.exe.disabled.” To carry out this change, users must ensure file extensions are visible.
Locate the Mshta file in both “C:\Windows\System32” and “C:\Windows\SysWOW64” directories, rename “mshta.exe” to “mshta.exe.disabled, ” while being logged in as an administrator. If necessary, take ownership of the file. Reversing this change is simply a matter of restoring the original filename.
As awareness of this vulnerability grows, it is likely that Microsoft will enhance modifications related to the application of MoTW in future updates. Always ensure your Windows operating system is updated, and keep default security features activated to potentially detect harmful scripts during their execution.
Leave a Reply