The Gospel lessons during the last Sundays of the Church Year and the season of Advent stress, among other things, being alert or watching and praying. One teaching that comes up in the readings at this time is that of the Anti-Christ.
One obvious understanding of the Anti-Christ is his role "against" Christ (see 1 Jn. 2:18-25, 4:1-4). There are many other passages that could be cited on this teaching but for purposes here John refers to a denial of Jesus coming in the flesh. A denial of Jesus coming "in the flesh" is of the anti-Christ.
In looking at what church fathers have said concerning Matthew 24:15ff other interesting understandings of the Anti-Christ come out. For example, he is referred to as "false word."
Historically, the Anti-Christ is located in a visible church by those who teach that the true church is invisible. If it is taught that the church is only invisible this is debatable, especially since faith accepts that Jesus came in the flesh. Another difficulty with an invisible church understanding is that Scripture speaks of the Holy Spirit (or Holy Ghost), who is invisible, as being attached to visible means. It may be argued that the same could be said of the Anti-Christ. While it is easy to attach the Anti-Christ to one office, location or place this is not as easy to defend.
Returning to the earlier theme of being alert or watching and praying one must consider that, as Christ is a unity of both human and divine natures so His Church is both invisible and visible. The Anti-Christ, likewise, works against Christ, His Gospel and His Church in both visible and invisible ways.
If we are to be alert then it is clear that we question attempts to place the Anti-Christ in only one place or Church when he could be active prowling around in our own back-yard.