Watch ye therefore, and pray always, that ye may be accounted worthy
to escape all these things that shall come to pass, and to stand before the Son of
man. - Luke 21:36
There are six passages that mention the mark of the beast in the book of Revelation.
And [the second beast] exerciseth all the power of the first beast before him, and causeth the earth and them which dwell therein to worship the first beast, whose deadly wound was healed. And he doeth great wonders, so that he maketh fire come down from heaven on the earth in the sight of men, And deceiveth them that dwell on the earth by the means of those miracles which he had power to do in the sight of the beast; saying to them that dwell on the earth, that they should make an image to the beast, which had the wound by a sword, and did live. And he had power to give life unto the image of the beast, that the image of the beast should both speak, and cause that as many as would not worship the image of the beast should be killed. And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name. Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six. - Revelation 13:12-18
AND
And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand, the same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb:
And the smoke of their torment ascendeth up forever and ever: and they have no rest day nor night, who worship the beast and his image, and whosoever receiveth the mark of his name. - Revelation 14:9-11
AND
And I saw another sign in heaven, great and marvelous, seven angels having the seven last plagues; for in them is filled up the wrath of God.
And I saw as it were a sea of glass mingled with fire: and them that had gotten the victory over the beast, and over his image, and over his mark, and over the number of his name, stand on the sea of glass, having the harps of God. - Revelation 15:1-2
AND
And the first went, and poured out his vial upon the earth; and there fell a noisome and grievous sore upon the men which had the mark of the beast, and upon them which worshiped his image. - Revelation 16:2
AND
And the beast was taken, and with him the false prophet that wrought miracles before him, with which he deceived them that had received the mark of the beast, and them that worshiped his image. These both were cast alive into a lake of fire burning with brimstone.
- Revelation 19:20
AND
And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshiped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years. - Revelation 20:4
Over the years, many have speculated on the nature of the Mark of the beast. Before we try to understand what the mark of the beast is here is a list of the things that the mark is not.
Many fundamental Christians abhor the social security number and the governmental control that comes with it. There is one positive note, my social security number separates me from all the other men with the name Jeffrey W. Barnes and at least one of them is a deadbeat dad. However, a society based on Christian ethics would not have this need for a Social Security Number.

The Mark of the Beast is not a Social Security Number because:
In every passage where it mentions the Mark of the Beast, it also mentions worshiping an image of the beast. In trying to understand the mark, we should also at the same time try to understand its association with its image.
And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: - Revelation 13:16
And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name. - Revelation 13:17
Read Revelation 13.
And he exerciseth all the power of the first beast [king or kingdom] before him, and causeth the earth and them which dwell therein to worship the first beast, whose deadly wound was healed. And he doeth great wonders, so that he maketh fire come down from heaven on the earth in the sight of men, And deceiveth them that dwell on the earth by the means of those miracles which he had power to do in the sight of the beast; saying to them that dwell on the earth, that they should make an image to the beast, which had the wound by a sword, and did live. And he had power to give life unto the image of the beast, that the image of the beast should both speak, and cause that as many as would not worship the image of the beast should be killed. And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name. Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six. - Revelation 13:12-18
Technically the death penalty may not be for refusing the mark of the beast; However, you must worship the image to receive the mark associated with it. It is in failing to worship the beast that one receives the death penalty.
And he had power to give life unto the image of the beast, that the image of the beast should both speak, and cause that as many as would not worship the image of the beast should be killed. And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: - Revelation 13:15-16