A droid attack flare, also known as an an alert flare, was an illuminated warning device used by the forces of the Galactic Republic during the Clone Wars. Firing a droid attack flare indicated that battle droids — of the Separatist Droid Army — had infiltrated or attacked Republic forces or territory.
During the Clone Wars, the surviving clone troopers of a Separatist attack on the Rishi Station listening post, Echo, Fives, and Hevy, fired a droid attack flare to warn Clone Commander Cody and Clone Captain Rex of the Separatists' infiltration. The two officers, who had been speaking to a disguised commando droid, were thus able to escape the ambush the commando droids had set up for them on the landing platform.