How can Attack Trees be used to identify and prioritize countermeasures?

Question

Accepted Answer

Attach a countermeasure to each attack path, cost it out, then prioritise the ones that block the most (or cheapest) paths.
Countermeasures in Attack Trees:

Shown as green boxes that block attack paths
Dotted lines = attack paths that are blocked by countermeasures

Example - "Guess Password" tree:

Attack Path
Countermeasure

Attempt logins
Throttle login attempts

Steal database from website
(needs mitigation)

Compute hashes
Use expensive hash algorithm

Overall
Use strong passwords

Process:

Build the attack tree
Identify countermeasures for each path
Cost-benefit analysis of implementing each countermeasure
Prioritize based on which countermeasures block the most/cheapest attack paths

Attack Path	Countermeasure
Attempt logins	Throttle login attempts
Steal database from website	(needs mitigation)
Compute hashes	Use expensive hash algorithm
Overall	Use strong passwords