Check file header before / after upload

Hello, 

I want to check the file header before ( or after ) I upload an Attachment ( File )
to an Sharepoint Item. 

Is there a way/solution to read the file header ( hex read ) ?

Based on the information I get from the "stream" I want to classify
the file/attachment in sharepoint ( e.g. wrong header / correct header )

Second solution:
I could also upload all files and the run a "check header tool" within Sharepoint.
Is this possible ?

Regards,
Steve