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ISC2 CC Practice Question: Uses a SIEM to correlate logs from multiple…
An organization uses a SIEM to correlate logs from multiple sources. A rule triggers when a user logs in from two geographically distant locations within a short time. What type of attack does this rule primarily detect?
⚠ Common exam trap
ISC2 often tests the concept of 'impossible travel' as a specific indicator of credential theft or session hijacking, and candidates mistakenly associate any unusual login pattern with brute-force attacks, failing to recognize that brute-force focuses on failed attempts, not successful logins from distant locations.
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
✓
Credential theft or session hijacking
The SIEM rule detects impossible travel — a user authenticating from two geographically distant locations within a time window too short for physical travel. This behavior strongly indicates that an attacker has stolen the user's credentials (credential theft) or taken over an active session (session hijacking) and is using them from a different location. The SIEM correlates authentication logs (e.g., from Active Directory, VPN, or web apps) with geolocation data (IP-to-location mapping) to flag this anomaly.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Denial of service attack
Why it's wrong here
Denial of service manifests as traffic volume or resource exhaustion degrading availability, whereas this rule correlates successful authentication events by location. DoS is tempting because SIEM rules do watch traffic anomalies, but no volume, rate or availability threshold is described here.
- ✗
Brute-force attack
Why it's wrong here
Brute-force detection keys on repeated authentication failures against one account, not on successful logins from separate locations. The rule matches impossible-travel patterns, so brute-force is tempting because both involve authentication events, but the geographic correlation of successful sessions points elsewhere.
- ✓
Credential theft or session hijacking
Why this is correct
Impossible-travel correlation relies on the physical impossibility of one user authenticating in two distant locations within the elapsed time. That axis distinguishes credential theft or session hijacking from volumetric attacks, which the rule cannot infer from authentication logs alone.
- ✗
Man-in-the-middle attack
Why it's wrong here
Man-in-the-middle interception occurs inline between client and server, so the SIEM would see session anomalies, certificate errors or unexpected proxies rather than two successful logins from distant geographies. The rule detects credential reuse across locations, which is a different indicator entirely.
Go deeper
Related to this question
Learn chapter
Physical Access Controls
Key term
SIEM
SIEM (Security Information and Event Management) is a system that collects and analyzes log data from across an IT environment to detect and respond to security threats in real time.
Key term
VPN
A VPN creates an encrypted tunnel over a public network to securely connect remote users or sites to a private network.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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