CISA Protection of Information Assets Practice Question
An IS auditor is examining how a data center protects its backup tapes while they are transported to an offsite vault. Management states that tapes are encrypted at rest using AES-256. Which of the following is the MOST important control the auditor should verify to protect the tapes during transit?
⚠ Common exam trap
The trap here is assuming encryption at rest fully protects backup tapes, when physical custody and tamper evidence are the controls that address the in-transit risk window.
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
✓
A chain-of-custody log with tamper-evident seals and dual custody is maintained for each shipment.
Because transport places media outside the controlled data center, the auditor should focus on physical custody controls. A documented chain of custody with tamper-evident seals and dual custody provides accountability and detects unauthorized access or substitution. Encryption protects confidentiality of data on the tape, but it does not prevent loss of the media or a denial of recovery capability, so custody controls are the most important complement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The offsite vault maintains a temperature and humidity-controlled environment.
Why it's wrong here
Environmental controls at the vault protect media from deterioration during storage, which is a valid availability control. However, they do not apply while the tapes are in the vehicle or in the hands of the courier. The auditor's focus is the transit phase, so vault environmental conditions do not address the risk of loss, theft, or tampering before the tapes arrive.
- ✗
The encryption keys are stored in a hardware security module (HSM) at the primary data center.
Why it's wrong here
Storing keys in an HSM at the primary site strengthens key protection, but it does not address the exposure of tapes in transit. If the transport vehicle is hijacked, the tapes leave with the ciphertext and the offsite recovery capability may be impaired if the HSM is destroyed or inaccessible. This control is relevant to key management, not to physical custody of media during transport.
- ✗
Backup jobs are scheduled outside business hours to reduce contention with production systems.
Why it's wrong here
Scheduling backups outside business hours is a performance and operations consideration. It reduces resource contention but has no bearing on whether tapes are protected while being moved to the offsite vault. The scenario specifically concerns transport protection, so backup window timing does not mitigate the risk of interception, loss, or unauthorized access during shipment.
- ✓
A chain-of-custody log with tamper-evident seals and dual custody is maintained for each shipment.
Why this is correct
During transit, tapes are outside the physically protected data center, so the primary risk is loss, theft, or substitution. A chain-of-custody log with tamper-evident seals and dual custody provides detective and preventive assurance that media were not accessed or swapped. This directly addresses the in-transit exposure and complements encryption by ensuring the physical media remain accounted for.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
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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 CISA 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 CISA exam.