Amen! in Jude 1:4, they are described as certain men whose condemnation was written about long ago have secretly slipped in among you. They are godless men, who change the grace of our God into a license for immorality and deny Jesus Christ our only Sovereign and Lord. In verse 12, they are described as spots in your love feasts, while they feast with you without fear, serving only themselves. They are clouds without water, carried about by the winds; late autumn trees without fruit, twice dead, uprooted. *This is not descriptive of saved believers, so there is no loss of salvation here.
Jude is exhorting believers to contend earnestly for the faith which was once for all delivered to the saints (vs. 3) because certain ungodly men who have crept in unnoticed. Jude further describes these ungodly men as ones who cause divisions, worldly-minded, devoid of the Spirit (vs. 19) In contrast to those who are called, sanctified by God the Father, and PRESERVED in Jesus Christ (vs. 1). Psalm 37:28 - For the Lord loves justice, And does not forsake His saints; They are PRESERVED FOREVER, But the descendants of the wicked shall be cut off.