Did you just stumble upon a file that is digitally signed by Open Source Developer, Mark Harmstone? If so, please read on.
You'll probably see Open Source Developer, Mark Harmstone when running the file. The publisher name shows up as the "Verified publisher" in the UAC dialog as the screenshot shows:

You can also view the Open Source Developer, Mark Harmstone certificate with the following steps:
Here's a screencap of a file that has been signed by Open Source Developer, Mark Harmstone:

As you can see in the screencap above, Windows states that "This digital signature is OK". This means that the file has been published by Open Source Developer, Mark Harmstone and that no one has tampered with the file.
If you click the View Certificate button shown in the screengrab above, you can see all the details of the certificate, such as when it was issued, who issued the certificate, how long it is valid, etc. You can also see the address for Open Source Developer, Mark Harmstone, such as the street name, city and country.
Certum Code Signing 2021 CA has issued the Open Source Developer, Mark Harmstone certificates. You can also view the details of the issuer by clicking the View Certificate button shown in the screenshot above.
These are the Open Source Developer, Mark Harmstone files I've collected, thanks to the FreeFixer users.At the moment there's no scan result available for any of the Open Source Developer, Mark Harmstone files, but they have been queued for scanning. Please reload this page in 5-10 minutes to check if the scan result is available.
| Detection Ratio | File Name |
|---|---|
| Queued for scan.. | btrfs.sys |
The analysis is done on certificates with the following serial numbers: