Help!! Very angry and aggressive cats!!?

Help!!! I have 7 cats and recently they have been acting very aggressive towards me, often hissing and jumping at my feet all at once for no reason! I don't know what to do!! They all do this now all of a sudden out of nowhere! Do you think cats are capable of conspiring against humans? Have my cats turned evil and are now plotting against me? Should I be scared? What do I do??