Second John is the Book of Truth & Love. The message of First John is personalized to an individual family in Second John. The deceiver and the antichrist are actively leading families astray. Godly families will not even receive or greet such false workers.
“Of John” is named for the author of the epistle.
Although the author simply calls himself “the elder,” the witness of the Church Fathers quotes this epistle and mainly ascribes it to John the son of Zebedee. Most valuable is the witness of Irenaeus (Against Heresies, 1.16.3). Jerome believed that John the Presbyter wrote 2nd & 3rd John, and is not the same as the Apostle John. Many liberal modern scholars follow Jerome, but most conservative scholars do not.