WMV File Security: Player Hijacking Risk

TL;DR

Yes, a specially crafted .wmv file can hijack Windows Media Player (WMP) and potentially run malicious code. This is usually done through exploiting vulnerabilities in the way WMP handles certain WMV features or by using deceptive scripting within the file itself. Keeping WMP updated, being cautious about where you get your files from, and using a good antivirus program are key to staying safe.

How a .wmv File Can Hijack Windows Media Player

1. Vulnerabilities in WMP: Older versions of Windows Media Player had known security holes. These allowed attackers to embed malicious code within a .wmv file that would execute when the file was played.
   • These vulnerabilities often related to how WMP processed specific codecs or features within the WMV format.
   • Microsoft regularly releases updates to patch these vulnerabilities, so keeping WMP current is vital.
2. Scripting Within .wmv Files: WMV files can contain scripting languages (like JScript) that are executed by WMP.
   • Attackers can embed malicious scripts into the file to perform actions like downloading other malware, modifying system settings, or stealing information.
   • These scripts aren’t always immediately obvious when looking at the file itself.
3. Metadata Exploitation: The metadata section of a .wmv file (information *about* the file) can sometimes be exploited.
   • Malicious code could be hidden within the metadata and triggered when WMP reads it.

Protecting Yourself

1. Keep Windows Media Player Updated: This is the most important step.
   • Windows Update: WMP updates are usually delivered through Windows Update. Make sure automatic updates are enabled.

     Control Panel > System and Security > Windows Update > Check for Updates

   • Microsoft Download Center: You can also manually check for updates on the Microsoft website if needed.
2. Be Careful Where You Get Your Files: Only download .wmv files from trusted sources.
   • Avoid suspicious websites, email attachments, or peer-to-peer file sharing networks.
   • If you’re unsure about a source, it’s best to avoid downloading the file altogether.
3. Use Antivirus Software: A good antivirus program can detect and block malicious .wmv files.
   • Make sure your antivirus software is up-to-date with the latest definitions.
   • Run regular scans of your computer to check for malware.
4. Disable Scripting (Advanced): You can disable scripting in WMP, but this may break some functionality.
   • This is not recommended for most users as it can affect legitimate WMV files.
   • If you choose to do this, research the implications carefully before proceeding.
5. Consider Alternative Players: Use a different media player that doesn’t have the same vulnerabilities as WMP.
   • VLC Media Player is a popular alternative known for its security and wide format support.

Checking a .wmv File (Basic)

You can’t reliably check a .wmv file for malicious code without specialized tools, but you can do some basic checks:

1. File Size: A very small .wmv file might be suspicious.
2. Source Reputation: Where did the file come from? Is it a trusted source?