This CHFI practice question tests your understanding of os and network forensics. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During a Linux forensic investigation, an analyst examines the file /var/log/auth.log and finds repeated entries with 'Failed password for root from 192.168.1.200 port 22 ssh2'. Which TWO conclusions can the analyst draw from this evidence?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The system is experiencing a brute-force attack on SSH
The log shows failed SSH login attempts for root from a specific IP, indicating a brute-force attack on SSH. The source IP is remote (not localhost). The attempts are unsuccessful (failed).
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 source IP 192.168.1.200 belongs to a local subnet
Why it's wrong here
192.168.1.200 is a private IP, but it could be from any network; it is not necessarily local to the system.
✓
The system is experiencing a brute-force attack on SSH
Why this is correct
Multiple failed login attempts from a single IP indicate a brute-force attack.
The attacker attempted to exploit a vulnerability in the SSH version
Why it's wrong here
The log shows password attempts, not exploit attempts.
✗
An unauthorized user successfully logged in as root
Why it's wrong here
The log shows 'Failed password', so logins were unsuccessful.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
The log shows password attempts, not exploit attempts.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CHFI question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CHFI subnetting questions on CIDR, address ranges, and subnet selection.
OS and Network Forensics — This question tests OS and Network Forensics — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The system is experiencing a brute-force attack on SSH — The log shows failed SSH login attempts for root from a specific IP, indicating a brute-force attack on SSH. The source IP is remote (not localhost). The attempts are unsuccessful (failed).
What should I do if I get this CHFI question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CHFI subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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