see the explanation for step by step solution.
Explanation:
Step 1: Analyzing the SFTP Log
The SFTP log provides a record of file transfer and login activities:
* User "sjames" logged in from several IP addresses:
* 192.168.10.32 and 192.168.10.37 (internal network IPs)
* 32.111.16.37 and 41.21.18.102 (external IPs)
* We see file alterations in the /var/www directory, which is commonly the web directory.
* Modified files: about_us.html, index.html
* Suspicious activity:
* 192.168.11.102 and 41.21.18.102 modified the files.
* 32.111.16.37 had failed login attempts, indicating possible unauthorized access attempts.
The most suspicious IP here is 41.21.18.102, as it's associated with direct file modifications, possibly indicating unauthorized access.
Step 2: Reviewing Netstat
The netstat output shows active connections and their states:
* IP 41.21.18.102 has an ESTABLISHED connection with port 22, commonly used for SFTP.
* IP 32.111.16.37 is also attempting connections, and 32.111.16.37 connections are in a TIME_WAIT state, showing prior connections were recently closed.
The netstat output reaffirms 41.21.18.102 is actively connected and potentially involved in malicious activities.
Step 3: Checking the HTTP Access Log
The HTTP Access log shows access to about_us.html:
* 32.111.16.37 repeatedly accessed /about_us.html with 404 errors, indicating attempts to reach non- existing pages.
* 41.21.18.102 accessed the 200 status code, showing successful page requests, but since this IP was modifying files directly on the server, it might be testing or verifying changes.
Again, 41.21.18.102 stands out as it matches both successful file modification and page request patterns, while 32.111.16.37 shows unsuccessful attempts.
Step 4: Selecting the IP of Concern
Based on the above analysis:
* answer: 41.21.18.102 should be the IP of concern due to its direct file modifications on critical web files (about_us.html, index.html).
Step 5: Identifying the Indicator of Compromise
Potential indicators include unauthorized file modifications:
* Modified index.html file is the correct answer, as it indicates direct changes to website content and is often a clear sign of compromise.
Step 6: Selecting Corrective Actions
To mitigate and prevent further compromise:
* Change the password on the "sjames" account: The account was used across various IPs, indicating potential account compromise.
* Block external SFTP access: Restricting SFTP to internal IPs only would prevent unauthorized external modifications. Since 41.21.18.102 was external, this would stop similar threats.
Summary
* IP of Concern: 41.21.18.102
* Indicator of Compromise: Modified index.html file
* Corrective Actions:
* Change the password on the sjames account
* Block external SFTP access
These selections address both the immediate security breach and implement a preventative measure against future unauthorized access.

The Diamond Model of Intrusion Analysis is a framework that describes the relationship between four components of a cyberattack: adversary, capability, infrastructure, and victim. It helps analysts understand the behavior and motivation of threat actors, as well as the tools and methods they use to compromise their targets12. References: Main Analytical Frameworks for Cyber Threat Intelligence, section 4; Strategies, tools, and frameworks for building an effective threat intelligence team, section 3.

The MITRE ATT&CK framework is specifically designed for tracking Tactics, Techniques, and Procedures (TTPs) associated with cyber threats. It provides a detailed matrix of known adversarial behaviors, which is useful for correlating SIEM data to known attack patterns. According to CompTIA CySA+, MITRE ATT&CK is an industry-standard framework for threat intelligence and behavior analysis, making it the ideal tool for tracking malicious IP addresses and understanding their tactics. Other options like OSSTMM, the Diamond Model, and OWASP do not focus on TTPs as directly as MITRE ATT&CK does.

After detecting a compromised email server and unusual network traffic, the next step in incident response is containment, to prevent further damage or spread of the compromise. References: CompTIA CySA+ Study Guide: Exam CS0-003, 3rd Edition, Chapter 5: Incident Response, page 197.

CVE details and IoCs are information that would most likely be required by the infrastructure team so that vulnerabilities can be remediated quickly. CVE details provide the description, severity, impact, and solution of the vulnerabilities that affect the servers. IoCs are indicators of compromise that help identify and respond to potential threats or attacks on the servers. References: Server and Workstation Patch Management Policy, Section: Policy; Patch Management Policy: Why You Need One in 2024, Section: What is a patch management policy?