Did you just run into a file that is digitally signed by Altium Limited? If that's the case, please read on.
You will probably notice Altium Limited when clicking to run the file. The publisher name shows up as the "Verified publisher" in the UAC dialog as the screenshot shows:

You can view the additional details from the Altium Limited digital signature with the following procedure:
Here is a screenshot of a file that has been digitally signed by Altium Limited:

As you can see in the screenshot above, Windows states that "This digital signature is OK". This implies that the file has been published by Altium Limited and that the file has not been tampered with.
If you click the View Certificate button shown in the screenshot above, you can examine all the details of the certificate, such as when it was issued, who issued the certificate, how long it is valid, and so on. You can also examine the address for Altium Limited, such as the street name, city and country.
Thawte Code Signing CA - G2 has issued the Altium Limited certificates. You can also see the details of the issuer by clicking the View Certificate button shown in the screenshot above.
The following are the Altium Limited files I've gathered, thanks to the FreeFixer users.Unfortunately I don't have any scan result from VirusTotal available for the Altium Limited files at the moment. The scan results will appear here as soon as a FreeFixer user uploads a file digitally signed by Altium Limited.
| Detection Ratio | File Name |
|---|---|
| Not available | AltiumMS.exe |
The analysis has been done on certificates with the following serial numbers: