Final answer:
An illegal attacker in volleyball is a back-row player or a libero attacking the ball above the net's height when in front of the attack line, or a front-row player attacking the ball above the net without part of the body above the net's height. Officials indicate the violation with a whistle and specific hand signals to identify the fault and the player responsible.
Step-by-step explanation:
An illegal attacker in volleyball refers to a player who commits a fault while executing an attack hit. This occurs when a back-row player or a libero, who are not allowed to complete an attack hit above the net's height when positioned in front of the attack line (also known as the 3-meter or 10-foot line), does so anyway. Moreover, a player is also considered an illegal attacker if they attack the ball completely above the top of the net while being front-row players but not having part of the body above the top of the net at the moment of the hit.
The violation is indicated by the official through a series of hand signals. The referee will blow the whistle to stop play and raise one arm vertically with the palm of the hand open, facing forward, and the other arm indicating the player at fault or the nature of the fault. The number of fingers displayed on the hand that indicates the fault corresponds to the nature of the illegal action per the standardized volleyball referee hand signals. It is crucial for both players and coaches to understand these signals to quickly adapt their gameplay and avoid further penalties.