It's also easy to fall to the temptation of blaming circumstances or your actions on such attacks. This is a list of possible symptoms of attacks taken from experiences and observations.
Someone acts suddenly and totally out of character.
Memory loss, especially on important matters.
Things feel stagnant. For example, a shop might suddenly stop having a clientele, and there is a distinctly uncomfortable or dead atmosphere.
Things suddenly stop working for no apparent reason.
Such as a car might stop working, but start working once the target of the attack moves on.