PostScript (.PS) File Viruses

TL;DR

Yes, a PostScript (.PS) file can contain a virus or malicious code. Because PostScript is a programming language, it can execute commands on your system when opened by a vulnerable application. While less common now than in the past, it’s still a risk, especially with older files or untrusted sources.

How PostScript Viruses Work

PostScript isn’t just for printing; it’s a full-fledged programming language. This means you can embed commands within a .PS file that do more than just draw shapes and text. These commands, if executed, could potentially harm your computer.

Steps to Protect Yourself

1. Be Careful with Untrusted Files: The most important step is to only open PostScript files from sources you trust completely. Avoid opening files received via email or downloaded from unknown websites.
   • If you must open a file from an untrusted source, do so in a safe environment (see Step 4).
2. Keep Your Software Updated: Ensure your PostScript interpreters (like Adobe Acrobat Reader or Ghostscript) are up-to-date. Updates often include security patches that address vulnerabilities.
   • Adobe products usually have an auto-update feature; enable it.
   • For Ghostscript, check the official website for updates: https://www.ghostscript.com
3. Disable PostScript Execution (If Possible): Some applications allow you to disable PostScript execution entirely.
   • In Adobe Acrobat Reader, this is often found in the Security Preferences. Look for options related to running external commands or JavaScript.
4. Use a Sandbox: Open suspicious .PS files within a sandbox environment. A sandbox isolates the file from your main system, preventing it from causing harm.
   • Virtual machines (like VirtualBox or VMware) are excellent sandboxes.
   • Windows Sandbox is built-in to some versions of Windows 10/11. You can enable it through ‘Turn Windows features on or off’.
5. Scan with Anti-Virus Software: While not always effective against sophisticated PostScript viruses, running a scan with up-to-date anti-virus software is still a good practice.
6. Examine the File (Advanced): If you’re technically inclined, you can open the .PS file in a text editor to look for suspicious commands. However, this requires knowledge of PostScript syntax and potential malicious code patterns.
   • Look for commands like exec or attempts to access system files.
   • Example of potentially dangerous command (do not execute!):

     /run {system("rm -rf /") } def

     This example is Linux-specific and would attempt to delete all files on the root directory. Malicious commands will vary.

What to do if you suspect a virus

1. Disconnect from the Network: Immediately disconnect your computer from the internet and any local networks to prevent further spread of potential malware.
2. Run a Full System Scan: Perform a full system scan with your anti-virus software.
3. Seek Expert Help: If you’re unable to remove the virus or are unsure how to proceed, consult a cybersecurity professional.