The church that Paul had established in Thessalonica had some who set out to "beguile" the faithful Christians in regards to the immediate return of Jesus (cf. I l Thess. 2:3). Paul explains to the Thessalonians that they are not to trouble themselves over this faulty information. He then gives them an idea as to when the Lord would come again. Before Jesus comes again, there will be a "falling away/' on the part of many Christians and the "son of perdition" will be exposed (Il Thess. 2:3). Note the connection between the 'falling away' and the "son of perdition" being exposed. The two events coincide even to the point to their being synonymous. Other synonymous terms for the "son of perdition" in the chapter are "man of sin" (Il Thess. 2:3) and "lawless one" (Il Thess. 2:8).
The "falling awaV' is associated with "the mystery of lawlessness" (Il Thess. 2:7) and "the working of Satan" (Il Thess. 2:9) as consequences of the son of perdition's work. Interestingly, Paul states that the "mystery of lawlessness doth already work" (Il Thess. 2:7). If then the "mystery of lawlessness" already works, the falling away has already begun, the son of perdition is already in existence in the days of Paul, and the day of the Lord is at hand.
The only other place in our Bible that uses the term "son of perdition" is John 17:12 where Jesus so labels Judas Iscariot. Jesus is praying in John 17 and the subject matter is unity through truth. Judas did not hold to the truth. Rather than being a son of God (Galatians 3:26; 1 John 3:1), Judas was of his father the devil and thereby a "son of perdition" (cf. John 8:44). Judas was not unlike many fallen away Christians today. Said ones are 'defectors' from the faith having 'departed' from the truth. The words 'defector' and 'departure' define the words "falling away' (Greek; apostasia; cf. LS 107). That which caused Judas (a son of perdition) to defect from the truth was his interest in the "mystery of lawlessness" which was the "working of Satan." Judas did not "receive the truth in love," but rather "had pleasure in unrighteousness" (Il Thess. 2:10-12).
Note that the son of perdition's work is "lawlessness" which is a "working of Satan" (Il Thess. 2:8-9). His work is further identified as one who "opposes and exalts himself against all that is called God or that is worshiped; so that he sits in the temple of God, setting himselfforth as God" (Il Thess. 2:4). To oppose, exalt against, and set one's self up as God is to reject everything that God stands for. Simply put, such a state of mind looks to make one's own way, standards, and law of life. This is who the "son of perdition" is. One who has left the faith and exercises a 'spirit' or disposition that opposes the teachings and authority of the Lord. He is directly associated with the Apostle John's use of "antichrist." John writes, "Little children, it is the last hour: and as ye heard that Antichrist cometh, even now have there arisen many Antichrists; whereby we know that it is the last houd' (2:18). The word "Antichrist" means 'against' Christ. Like the son of perdition, Antichrist is the spirit, disposition, character, attitude, or state of mind of one who would reject the authority of Jesus Christ and His teachings.
Both the spirit of the son of perdition and Antichrist exist today. Many of God's people today hold dear a beloved false teacher over the word of God because they love to be comforted in their sin. Through such 'spirits,' attitudes, or dispositions of opposition, the Lord "sends a working of error, that they (those who received not the love of the truth) should believe a lie" (Il Thess. 2:10-11). So God winnows the wheat of mankind. As God used Judas Iscariot's disposition of sin (John 17:12) along with Pharaoh of Egypt (Romans 9:17-18), the Asyrian army (Isaiah 10:5-14), and the Babylonians under Nebuchadnezzar (Jeremiah 25:8-14) to accomplish His own ends even so the Lord uses the "son of perdition" against those who "believe not the truth, but had pleasure in unrighteousness" (Il Thess. 2:12). God did not make any of these men or nations evil, they made the choice themselves (cf. James 1:13ff). Their true love was their sin. Jeremiah records, "the prophets prophesy falsely, and the priests bear rule by their means; and my people love to have it so:" (Jeremiah 5:31). Lovers of error are exposed as well as the lovers of truth when the gospel is preached.
Yes, the spirit of the son of perdition and Antichrist exist today. Those who deny the authority of Christ by word and or deed do make it manifest that they are sons of the devil rather than a son of God; i.e., a "son of perdition" (cf. Il John 9-11). The son of perdition and spirit of antichrist are equivalents. Such represents an attitude of rebellion against the authority of Christ. This being so, the Lord's coming is surely at hand today as it was during the days of Paul and the Thessalonian's life. We are living in the last days (Il Pet. 3:3ff).