What is MIME type "application/vnd.ms-pki.seccat"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

The MIME type application/vnd.ms-pki.seccat represents a Microsoft security catalog. It is used for files that store digital signatures and cryptographic hashes. These files help Windows verify the integrity of drivers and system files.

Files with this MIME type use the extension CAT. They carry the information required to check if software has been altered or corrupted. This aids in preventing untrusted code from running on your system.

Integrity Verification: Assures that system and driver files have not been tampered with.
Code Signing: Confirms the authenticity of software components.
Security Checks: Enables Windows to perform automated security validations during installations and updates.

For more detailed information on how these files contribute to system security, visit the Microsoft Security Catalog Files documentation.

Associated file extensions

.cat

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: application/vnd.ms-pki.seccat

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="application/vnd.ms-pki.seccat">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');    
    
    http.createServer((req, res) => {    
      res.setHeader('Content-Type', 'application/vnd.ms-pki.seccat');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.cat

FAQs

What is the purpose of the application/vnd.ms-pki.seccat MIME type?

This MIME type identifies Windows Security Catalog files, which typically use the .cat extension. These files act as a digital address book containing cryptographic hashes for a collection of files, allowing Windows to verify that drivers or software components have not been tampered with since they were signed.

How do I configure IIS to serve .cat files correctly?

To serve these files on Microsoft IIS, open the MIME Types feature in the IIS Manager. Click Add, set the file extension to .cat, and set the MIME type to application/vnd.ms-pki.seccat. This ensures clients receive the correct headers when downloading driver packages or updates.

Can I view the contents of a file with this MIME type?

Yes, but usually only on Windows systems. If you double-click a .cat file in Windows Explorer, the OS displays the Security Catalog interface, where you can view the signer information and the list of file hashes included in the catalog. You cannot edit these files with a text editor.

How do I add support for this MIME type in Apache or Nginx?

For Apache, add the line AddType application/vnd.ms-pki.seccat .cat to your .htaccess or config file. For Nginx, add application/vnd.ms-pki.seccat cat; inside the types { ... } block of your nginx.conf or mime.types file.

Why am I getting a 'missing catalog file' error during driver installation?

This error occurs when Windows attempts to verify a driver's digital signature but cannot find the associated .cat file. Without the file serving as application/vnd.ms-pki.seccat, Windows cannot confirm the driver's integrity and may block the installation to protect the system.

Are files with the application/vnd.ms-pki.seccat type dangerous?

Generally, no. A .cat file contains data hashes and signatures, not executable code, so it cannot run a virus itself. However, hackers might try to forge or alter catalog files to hide malware, so it is vital that the catalog itself has a valid digital signature from a trusted certificate authority.

How are these files created by developers?

Developers generate these files using the MakeCat tool found in the Windows SDK. The process typically involves creating a text-based Catalog Definition File (.cdf) first, which is then compiled into the binary .cat file identified by this MIME type.

General FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.