Factors of threat can include: surprise, means of attack, target of attack, foreknowledge of response, and significant dates.

• Surprise—Terrorists generally operate as “lone wolves” or in a cellular structure. The cells consist of a limited number of people having knowledge of intent or plans. This restricts the community’s ability to anticipate the attack.
• Means of attack—Terrorists may choose Toxic Industrial Chemicals (TIC), chemical WMD agents, biological WMD agents, radiological WMD, or Improvised Explosive Devices (IED). IED is the most likely means of attack.
• Target of the attack—Targets are generally chosen due to of the possibility of mass casualties. However, disrupting critical infrastructures can have a large psychological impact on society. Symbolic targets cause people to believe the government cannot protect the country from a terrorist attack.
• Foreknowledge of the community response—Terrorists choose to observe, plan, and attack with the fewest number of people possible. This limits the community’s ability to have prior knowledge of an attack. Terrorists will also understand the community’s capability to respond to an attack, and will exploit the community’s weaknesses.
• Significant dates—Terrorist often coordinate attacks to coincide with previous attacks or significant anniversaries.