Did you just run into a file that has been digitally signed by Giant Matrix Limited? If so, please read on.
You will probably see Giant Matrix Limited when running the file. The publisher name is then displayed as the "Verified publisher" in the UAC dialog as the screengrab shows:

You can also view the Giant Matrix Limited certificate with the following procedure:
Here is a screenshot of a file signed by Giant Matrix 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 Giant Matrix Limited and that no one has tampered with the file.
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, etc. You can also examine the address for Giant Matrix Limited, such as the street name, city and country.
Thawte Code Signing CA - G2 has issued the Giant Matrix Limited certificates. You can also view the details of the issuer by clicking the View Certificate button shown in the screenshot above.
These are the Giant Matrix Limited files I've collected, thanks to the FreeFixer users.
| Detection Ratio | File Name |
|---|---|
| 0/44 | ATFREE~1.DLL |
| 0/70 | ATFREE~1.DLL |
| 0/44 | aflfile64.sys |
The detection percentage is based on that I've collected 158 scan reports for the Giant Matrix Limited files. 0 of these scan results came up with some sort of detection. If you like, you can review the full details of the scan results by examining the files listed above.
The analysis has been done on certificates with the following serial numbers: