After a May 4 suicide bombing attack in Arbil, Iraq that inflicted about 100 casualties, the Joint Chiefs of Staff stated on May 5 that the Zaytun unit has raised its terror alert level from Amber (Tension) to Red (Threat).
The terror alert rating system is classified into four levels: Common (Green), Tension (Amber), Threat (Red), and Emergency (Black). The higher the level, the more likely a terror attack will occur.