What is an External ID in the context of AWS IAM cross-account role assumption, and why does Prisma Cloud require it?
The External ID is a value the trusting account requires in the AssumeRole call, binding the session to the specific third party and blocking the confused deputy problem. Prisma Cloud mandates it so its cross-account access cannot be replayed by another customer.
Why this answer
An External ID is a unique, customer-defined string passed in the AWS STS AssumeRole API call to prevent the confused deputy problem. When a third-party tool like Prisma Cloud assumes a role in a customer's AWS account, the External ID ensures that only the intended customer can authorize that assumption, preventing another customer from tricking the third party into accessing resources. Prisma Cloud requires it to securely assume cross-account roles without sharing long-term credentials.
Exam trap
The trap is confusing External ID with a secret key or account number; candidates must remember it is a non-secret unique identifier specifically for preventing the confused deputy problem in cross-account role assumption.
How to eliminate wrong answers
Option A is wrong because External ID is not a password for S3 encryption; S3 encryption uses KMS keys or SSE. Option B is wrong because it is not an API key for agent authentication; Prisma Cloud agents use different credentials. Option C is wrong because it is not the AWS management account number; the account number is a separate identifier used in the trust policy.