[CPA QUESTION] How do CPA companies know your filling out there offers?

[yoyolefou]

Ok, so I have a simple question.
How do CPA companies know that you are filling out there offers?
Specially talking SOI survey offer/Email submits
Is it your IP address that give you away or MAC address or something else?
Is there a technique that allows us a solution workaround?
Looking forward to all answers
Thanks in advance