CISM Incident Management Practice Question
An organization has experienced a ransomware attack that encrypted critical servers. The incident has been classified as P1. Which of the following is the FIRST action the incident response team should take according to the IR plan?
⚠ Common exam trap
CISM often tests the misconception that root cause analysis or evidence preservation should come before containment; the trap is prioritizing investigation over stopping the active threat, which can lead to wider compromise.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Contain the incident by isolating affected systems from the network.
According to standard incident response (IR) frameworks such as NIST SP 800-61 and CISM best practices, the first priority after detecting a P1 incident like ransomware is containment. Isolating affected systems from the network prevents the malware from spreading to other critical servers and limits the blast radius. Only after containment should the team proceed with eradication, recovery, and forensic analysis.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Perform root cause analysis to determine how the ransomware entered.
Why it's wrong here
Root cause analysis happens after containment and eradication; performing it while ransomware is still active lets additional servers be encrypted. It is the correct later phase once the threat is isolated and systems are being restored.
- ✗
Begin forensic imaging of all affected servers for evidence preservation.
Why it's wrong here
Forensic imaging preserves evidence but does not stop the ransomware from continuing to encrypt servers, so containment must precede it. Imaging is tempting because evidence preservation is a recognised IR step, yet it belongs after the threat is contained, not as the first P1 action.
- ✗
Notify the CEO and activate the crisis management team.
Why it's wrong here
Notification and crisis-team activation follow containment; executing the IR plan's first P1 step means stopping the encryption from spreading across remaining servers. Escalation is correct once containment is underway and executive decisions on disclosure or ransom are required.
- ✓
Contain the incident by isolating affected systems from the network.
Why this is correct
Isolating encrypted servers halts lateral spread and further encryption, preserving remaining evidence and business functions before eradication or recovery begins. Containment is the prescribed first phase for a P1 ransomware event, since every minute of continued network access increases damage.
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
Go deeper
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISACA exam blueprint
This CISM practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISM exam.