Here are 8 Signs of Spiritual Warfare (spiritual attack) taking place. Being alert to these can help you weigh up whether or not a situation is being affected by spiritual warfare:
Changes for the Worse in the Areas of Health, Finances, or Relationships
An Atmosphere of Pressure or Oppression
Severe Discouragement
Crippling Condemnation
Intimidation and fear
Confusion
Temptation to Sin
A Battle in the Mind
The enemy is trying to get us to believe messages that go against God's promises. But you must recognize what's happening is not you, it's something external coming against you.
The enemy is using discouragement and intimidation
There are threats involved
There is a blatant distraction
The enemy is sowing seeds of disunity and division within the Body and between brothers and sisters in the Lord (added by Raimer)