The entire world is looking for a physical manrk, either a tattoo or a microchip.

A microchip most likely will be used but that is not the mark.

The mark (according to the bible) is in the right hand or on the forehead.

According to Galatians 2:9 "gave the right hands of fellowship", also knowledge is in the head.

It's like this...

you know the truth about the Antichrist and accept him anyway - that's knowledge, or by blind ignorance, don't care but will accept him any way - that extending the right hand of fellowship.