In order to figure out what the mark is, we first need to know who and what is the Beast. The two legs of iron of the great statue in Daniel 2 and the Beast that rises up out of the sea (Revelation 13) are symbolic of the same thing that the fourth animals in Daniel 7 represents. Daniel 7's dreadful and strong animal has teeth of iron and ten horns, making it the most fearsome animal seen in Daniel's dream. It represents the Roman Empire, including its various resurrections, such as the Holy Roman Empire of the Middle Ages.
The End Time Identity
The term 'Beast' can refer to either an empire as a whole or the dictator leading it, just as a king represents his country symbolically (cf. Daniel 7:17-18, where "king" and "kingdom" are interchangeable). The end time world power, who will enforce a mark on all people, will be the current European Union (possibly minus a few smaller countries) or the dictatorial person who heads it. What can be confusing is that the SECOND beast of Revelation 13 (verses 11-18) is the false prophet who leads a religious institution or church. If we use what Revelation chapter 17 to 18 says about a "woman riding the Beast," this second 'animal' is also symbolized by a woman. Ask yourself what church became unified with the state during the Middle Ages and even with the Roman Empire before it fell? What church had great influence over kings and emperors?
Identity of the woman
If we use history as our guide to interpret these above symbols we arrive at the conclusion that the Roman Catholic church, both in the past and near future, was and will be in an unrighteous alliance with the European-based government that supports it. It may sound incredible and highly unlikely, but the union of church and state that characterized the Middle Ages WILL be reborn fully in the years just ahead of us. The church, or the person who represents her, will publicly perform demonic miracles that will deceive almost everyone into believing the power of God backs him.
Meaning of the Number
What could the number 666 referred to in Revelation 13 possibly mean? Biblically, the number 6 represents incompleteness or imperfection, as it is one less than seven which is the number of completeness (e.g. seven days in a week). The meaning of three 6's, or 666, therefore, points to someone or something being imperfect or limited in three ways or three times. That is why it's the number of a man, since man is necessarily imperfect compared to God. A key understand that will help us further interpret this number arises from an interesting aspect of the Greek language (which was the original written language of the New Testament). You may have noticed certain clocks that use archaic numbers on their faces such as V or X. Most people know that V represents the number 5 and X the number 10. The Greek letters of the alphabet can also represent numbers.
In Revelation 13 it says to count or calculate the number of the beast (Revelation 13:18). It needs to be added up to mean something. It should not surprise those who have studied some Bible prophecy that the word for a "Latin man" in Greek (Lateinos) is made up of letters that add up to 666! This confirms that Rome is the first beast of Revelation 13 and the fourth beast of Daniel 7.
We know WHO or WHAT the Beast is, but what is its MARK? Notice that nothing is said in Revelation 13 about high tech items such as computers and government issued photo IDs, although it's possible that such tools may be used to enforce this special identification in the future. Notice that it (Revelation 13:16) appears on the right hand or on the forehead of people. The right hand is symbolic of a man's ability to do something that he thinks about. The forehead is symbolic of the brain and mind, where thoughts, good and bad, come from. Notice also that it will be popular and that most people will accept it. They will take the identifying sign because they want to buy or sell, which includes their labor and services at work to their employers, not just product and service purchases in stores (verse 17). Another clue to what the mark of the beast actually is comes from the fact that people who obey God's law DO NOT receive it.
and those who worship the beast and his image, and all who receive the mark of his name, have no rest day and night. 12. Here is the patience of the saints; here are the ones who keep the commandments of God and the faith of Jesus (Revelation 14:11-12)
Those who accept the identifying sign of Satan's system are in a different group than those keeping God's commandments (Revelation 15:2-3). Satan will attack those true Christians who are keeping the Eternal's Holy laws (Revelation 12:17).
A mark or sign identifies who someone is or what something is such as a logo or trademark of a corporation. Notice that God's sign (keeping the commandments and Jesus' faith) is opposed to the Beast's mark. Exodus 32 and verse 13 says that the Biblical Sabbath (the seventh day of the week) is a "sign" between God and His people. Furthermore, God's law is considered to be on people's foreheads (Deuteronomy 6:1, 6-8) and hands (Deuteronomy 11:18; Exodus 13:9). Which of God's Ten Commandments are the most ignored? Which one can most people be easily deceived over since it can't be argued that its exists by natural law reasoning? It is the fourth commandment. People either say that Jesus abolished it or that it was transferred to Sunday from Saturday. The Catholic Church even boasts that, by its own authority, it changed the Sabbath to Sunday. In Daniel 7:25 a prophecy is given that the little horn, which represents the end time false church, will want to change times and laws. In this case, they changed the law concerning the time of the Sabbath rest without Biblical authorization.
Given the evidence above, we are lead to the conclusion that the breaking of God's law, especially His seventh-day Sabbath rest, is the mark of the Beast. It will be enforced by the civil government, just like other religious-based or related laws have and are enforced today.