Mission brief · N-401

Tier 3 analyst on the incident response bench

Tier 3 — deep host and forensics

Business important

Track default

You are acting as

the break-glass IR account `svc-ir`, checked out of the vault for this incident — never the compromised identity

How you got here

The detection fired in the EDR console. You opened a live-response session from that detection, so your shell rides the EDR agent channel — containing the host will *not* cut you off, which is exactly why you contain from here rather than over SSH.

Your access

EDR console (detections + live response)
Endpoint detection & response
- Read the detection and process tree
- Look up host criticality, owner and VIP flags
- Open a live-response session on the host
- Contain the host over the agent channel
- Not yours: Disable user accounts (that's the identity team)
- Not yours: Delete evidence
Live-response shell on the affected host
Host shell session
- Read the filesystem, logs and running state
- Collect a triage package
- Not yours: Reboot or reimage without owner approval

What's at stake

The affected host

Owner: The system's business owner, named on the asset record

Containing a host you haven't identified can stop revenue. Check criticality and owner before you isolate anything.

Rules of engagement

You may act alone

Investigate from the live-response session
Collect evidence and triage packages
Contain a standard-criticality host

Ask a human first

Containing a mission-critical host — asset owner and on-call manager first
Disabling a user identity — identity team, and HR/legal if it looks like an insider

How much help do you want?

Objectives stay open and every step explains why it matters before it tells you what to run. Hints are free.

Graded case walkthrough

Open a lab as a live case and advance it one node at a time. The score beside each step is the lab rubric re-evaluated against what the engine actually did.

Lab

Audit finding NW-AUD-114 says nobody can demonstrate the corporate VLAN is separated from the server farm, the DMZ and the internet. You get a seat on an ordinary endpoint and nothing else, so prove the design from the wire, including the endpoint holding a session it should not have.

Range guide

Guided

Every step explains why it matters before it tells you what to do. Reasoning is free in guided mode.

Prove it

1. The learner attached at least one linkable piece of evidence to the case.
Why this step: The learner attached at least one linkable piece of evidence to the case. It carries 10 points on the investigation dimension.
2. Nothing was changed in the estate before evidence had been gathered.
Why this step: Nothing was changed in the estate before evidence had been gathered. It carries 10 points on the investigation dimension.
3. The analyst worked the live network from the endpoint instead of describing it from memory.
Why this step: The analyst worked the live network from the endpoint instead of describing it from memory. It carries 10 points on the investigation dimension.
4. The connected subnet was read from the interface and routing table.
Why this step: The connected subnet was read from the interface and routing table. It carries 10 points on the investigation dimension.
5. Inter-VLAN routing was proven with a trace rather than assumed.
Why this step: Inter-VLAN routing was proven with a trace rather than assumed. It carries 10 points on the investigation dimension.
6. The resolver in use was identified from the host's own configuration.
Why this step: The resolver in use was identified from the host's own configuration. It carries 10 points on the investigation dimension.
7. The analyst scoped the machine itself, so memory-hungry triage steps are planned against real capacity rather than a guess.
Why this step: The analyst scoped the machine itself, so memory-hungry triage steps are planned against real capacity rather than a guess. It carries 3 points on the investigation dimension.
8. Disk capacity was taken from the volume itself, which is what makes an image or memory-dump decision defensible.
Why this step: Disk capacity was taken from the volume itself, which is what makes an image or memory-dump decision defensible. It carries 3 points on the investigation dimension.

Decide and act

1. The workflow reached a terminal success state on the graded run.
Why this step: The workflow reached a terminal success state on the graded run. It carries 20 points on the behavior dimension.
2. A reversible action passed through a human approval gate.
Why this step: A reversible action passed through a human approval gate. It carries 15 points on the safety dimension.
3. No non-idempotent operation was retried without an idempotency key.
Why this step: No non-idempotent operation was retried without an idempotency key. It carries 10 points on the efficiency dimension.
4. Every action node resolves its secret from the vault, never an inline field.
Why this step: Every action node resolves its secret from the vault, never an inline field. It carries 10 points on the configuration dimension.
5. No innocent asset in the alert batch was contained, disabled or revoked.
Why this step: No innocent asset in the alert batch was contained, disabled or revoked. It carries 15 points on the behavior dimension.
6. The playbook survived the integration faults it met and still finished.
Why this step: The playbook survived the integration faults it met and still finished. It carries 15 points on the configuration dimension.
7. The single permitted egress path was located, which is what makes the rule base enforceable.
Why this step: The single permitted egress path was located, which is what makes the rule base enforceable. It carries 10 points on the behavior dimension.
8. The audit finding is answered with a specific deny rule, by number.
Why this step: The audit finding is answered with a specific deny rule, by number. It carries 15 points on the behavior dimension.
9. The endpoint holding an unauthorized external session is isolated at end state.
Why this step: The endpoint holding an unauthorized external session is isolated at end state. It carries 15 points on the behavior dimension.

Write it up

1. The case carries an analyst closure note explaining the outcome.
Why this step: The case carries an analyst closure note explaining the outcome. It carries 10 points on the explanation dimension.
2. The unauthorized egress was attributed to a specific host on the analyst's own VLAN.
Why this step: The unauthorized egress was attributed to a specific host on the analyst's own VLAN. It carries 10 points on the explanation dimension.
3. A written segmentation record was filed: zones, routing path, permitted egress and the exception found.
Why this step: A written segmentation record was filed: zones, routing path, permitted egress and the exception found. It carries 10 points on the explanation dimension.

Your cases

No cases opened yet.