Terror alert system
Terror alert systems are standardised emergency population warning systems for describing and disseminating information about terrorism-related threats. They became more popular after the September 11 attacks on the United States in 2001.
Australia
National Counter-Terrorism Alert Level
- Low - terrorist attack is not expected
- Medium - terrorist attack could occur
- High - terrorist attack is likely
- Extreme - terrorist attack is imminent or has occurred
Administered by the Federal Attorney-General's Department.
France
Main article: Vigipirate
Plan Vigipirate
- Yellow - to stress vigilance
- Orange - to warn of terrorist action
- Red - to warn of serious attempts
- Crimson - to warn of major attempts
United Kingdom
Main article: UK Threat Levels
- Low - an attack is unlikely
- Moderate - an attack is possible, but not likely
- Substantial - an attack is a strong possibility
- Severe - an attack is highly likely
- Critical - an attack is expected imminently
Administered by the Joint Terrorist Analysis Centre
United States
Homeland Security Advisory System
- Low - Low risk of terrorist attacks
- Guarded - General risk of terrorist attacks
- Elevated - Significant risk of terrorist attacks
- High - High risk of terrorist attacks
- Severe - Severe risk of terrorist attacks
Administered by the Department of Homeland Security