The working group must establish criteria for evaluating the likelihood of a threat agent being used to commit a terrorist act in or through a customer's operation or facility. The exact evaluation criteria will depend on the specific facilities and operations being considered. The following criteria were used in a recent threat assessment; they provide an illustration of the considerations that typically apply in evaluating the severity of an incident.

Ability to access materials 

For the Ability to Access Materials criterion, a high rating was awarded to threat agents that were easy to access, whereas a low rating was awarded to threat agents that were difficult to access. In this context, a rating of “high” represents a higher level of concern because a threat agent is relatively readily available for use by a terrorist, while a rating of “low” equates to a lower level of concern where a threat agent is highly controlled and thus much less likely to be available to a terrorist. For all threat agent scenarios, five Ability to Access Materials checklist items were considered as potentially applicable. In assigning overall ratings, working group members exercise professional judgment in how the various checklist items are weighted based on knowledge of which items are most significant for the agent being evaluated.

Checklist Item	Descriptors
Threat agent cost	High = < $100 K, Medium = $1 M, Low = multi-$M
Threat agent availability	High = commercially, Medium = within restricted community, Low = only in high security facility
Possession	High = known, Medium = suspected, Low = unknown/short storage life
Component availability	High = readily, e.g., local hardware store, Medium = somewhat restricted, e.g., most school labs, Low = difficult to obtain, e.g., only from ATCC, CWC scheduled
Difficulty of cultivation/manufacture	High = simple, e.g., can be made in a kitchen, Medium = modest facility, e.g. can be made in a drug lab, Low = very difficult, e.g., requires a chemical plant

Viability for use in the customer's facility or operations 

For the Viability for Use in the Customer Environment Facility or Operations, high ratings were awarded to threat agents that were easy to introduce into the customer's process stream and were long-lived in the customer environment. Low ratings were awarded to threat agents that were difficult to introduce into the process stream or were short-lived in the customer environment. For all threat agent scenarios, three checklist items were considered as potentially applicable.

Checklist Item	Descriptors
Level of technology/knowledge needed to construct a device that can be packaged within customer size and weight restrictions or placed within a customer facility	High = can be done by a high school graduate with hardware store parts, Medium = college student with some specialized parts or design, Low = requires Ph.D. or sophisticated design
Likelihood of detection using existing practices and systems	High = will not be detected by postal workers or existing sensors before incident, Medium = may be detected, Low = probably will be detected before incident
Durability/stability of threat agent in the postal system	High = Remains functional indefinitely in ambient air, Medium = remains functional for moderate length of time, Low = Remains functional only in a controlled environment

Appeal for use by the terrorist

For the Appeal for Use by the Terrorist criterion, high ratings were awarded to threat agents that were judged to have high appeal to terrorists, whereas low ratings were awarded to threat agents that were judged to have lower appeal to terrorists. For all threat agent scenarios, four checklist items were considered as potentially applicable.

Checklist Item	Descriptors
Appropriateness of customer's facilities and operations to terrorist means	High = value of Customer targets match threat agent and means of delivery, Medium = some mismatch, Low = threat agent and means much more valuable than Customer targets
Safety during preparation and packaging	High = handled with minimal precautions., Medium = expensive or complicated precautions, Low = very complicated precautions requiring expensive infrastructure
History	High = Multiple known or threatened incidents, Medium = single known or threatened incident, Low = Never used or threatened
Expected psychological impact	High = national impact, e.g., live cable coverage, lead on network news, Medium = regional impact, e.g., front page on major papers in region, Low = local impact only, e.g., coverage inside major papers