Scripture tells us that angels and demons (I want particularly to mention Satan) are spiritual creatures but also that they are individuals gifted with intelligence, will, freedom, and initiative. Those modern theologians who identify Satan with the abstract idea of evil are completely mistaken. Theirs is true heresy; that is, it is openly in contrast with the Bible, the Fathers, and the Magisterium of the Church. The truth about Satan was never doubted in the past; therefore, there are no dogmatic definitions in this respect with the exception of the following statement of the Fourth Lateran Council: "The devil [that is, Satan] and the other demons were created good by God; but they became evil through their own fault." Whoever denies Satan also denies sin and no longer understands the actions of Christ.

http://www.ignatiusinsight.com/features/framorth_excerpt1_aug04.asp

I believe that Pope Leo XIII, in a vision that will be detailed in the appendix of this chapter [pages 37-39] received a prophetic warning concerning this demonic attack on our times.

He did and he composed a prayer which should be said by true Catholics daily.

PRAYER TO ST. MICHAEL THE ARCHANGEL
O Glorious Archangel St. Michael, Prince of the heavenly host, be our defense in the terrible warfare which we carry on against principalities and powers, against the rulers of this world of darkness, spirits of evil.

Come to the aid of man, whom God created immortal, made in His own image and likeness, and redeemed at a great price from the tyranny of the devil.

Fight this day the battle of the LORD, together with the holy angels, as already thou hast fought the leader of the proud angels, Lucifer, and his apostate host, who were powerless to resist thee, nor was there place for them any longer in Heaven.

That cruel, that ancient serpent, who is called the devil or Satan, who seduces the whole world, was cast into the abyss with his angels.

Behold, this primeval enemy and slayer of men has taken courage. Transformed into an angel of light, he wanders about with all the multitude of wicked spirits, invading the earth in order to blot out the name of God and of His Christ, to seize upon, slay and cast into eternal perdition souls destined for the crown of eternal glory.

This wicked dragon pours out, as a most impure flood, the venom of his malice on men of depraved mind and corrupt heart, the spirit of lying, of impiety, of blasphemy, and the pestilent breath of impurity, and of every vice and iniquity.

These most crafty enemies have filled and inebriated with gall and bitterness the Church, the spouse of the immaculate Lamb, and have laid impious hands on her most sacred possessions.

In the Holy Place itself, where has been set up the See of the most holy Peter and the Chair of Truth for the light of the world, they have raised the throne of their abominable impiety, with the iniquitous design that when the Pastor has been struck, the sheep may be scattered.

Arise then, O invincible Prince, bring help against the attacks of the lost spirits to the people of God, and give them the victory. They venerate thee as their protector and Patron; in thee holy Church glories as her defense against the malicious power of hell; to thee has God entrusted the souls of men to be established in heavenly beatitude.

Oh, pray to the God of peace that He may put Satan under our feet, so far conquered that he may no longer be able to hold men in captivity and harm the Church.

Offer our prayers in the sight of the Most High, so that they may quickly conciliate the mercies of the LORD; and beating down the dragon, the ancient serpent, who is the devil and Satan, do thou again make him captive in the abyss, that he may no longer seduce the nations.  Amen.

V. Behold the Cross of the LORD; be scattered ye hostile powers.
R. The Lion of the tribe of Judah has conquered the root of David.
V. Let Thy mercies be upon us, O LORD.
R. As we have hoped in Thee.
V. O LORD, hear my prayer.
R. And let my cry come unto Thee.

Let us pray.

O God, the Father of our LORD JESUS Christ, we call upon Thy holy Name, and as suppliants, we implore Thy clemency, that by the intercession of Mary, ever Virgin Immaculate and our Mother, and of the glorious Archangel St. Michael, Thou wouldst deign to help us against Satan and all other unclean spirits, who wander about the world for the injury of the human race and the ruin of souls.  Amen.