Investigating a Malware Attack
A Real-World Incident Response
As a junior security administrator, my primary responsibility was to perform initial triage on security alerts and escalate high-priority incidents to senior analysts.
In this case study, I investigated an alert triggered on our Security Onion system, indicating a potential malware infection. This blog post walks through my approach to analyzing the incident, understanding the attack methodology, and recommending mitigation strategies.
The Incident: Initial Alert
A security alert was generated for an event with the following details:
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Source IP Address: 188.124.9.56 (Identified as malicious in VirusTotal)
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Destination IP Address: 192.168.3.35 (A networked device, possibly a router admin interface)
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Destination Port: 1035 (Often associated with Trojan communications)
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Event Message: ET TROJAN JS/Nemucod.M.gen downloading EXE payload
Indicator of Compromise (IoC) Analysis
Upon further investigation, the source IP was flagged for distributing malware, while the event message suggested a Trojan downloader named Nemucod, known for delivering ransomware or banking Trojans.
The Cyber Kill Chain Breakdown
To analyze this attack methodically, I mapped it to the Cyber Kill Chain framework:
| Phase | Findings |
|---|---|
| Reconnaissance | The attacker may have used social engineering (e.g., phishing emails) or port scanning to identify vulnerabilities. |
| Weaponization | A seemingly legitimate link or attachment was likely crafted to appear as a work-related document. |
| Delivery | The attack was likely executed through a phishing email, a malicious ad, or a compromised website. |
| Exploitation | Nemucod executed JavaScript on the victim’s system, initiating a malware download. |
| Installation | The malware was installed through JavaScript execution, allowing further payload deployment. |
| Command & Control (C2) | The infected system contacted the attacker’s C2 server for additional instructions and downloads. |
| Actions on Objectives | Potential data exfiltration, credential harvesting, or further system compromise. |
Adversarial Motivation
The attack’s primary objectives were likely:
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Deploying additional malware (e.g., ransomware, banking Trojans, spyware)
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Gaining unauthorized access to sensitive systems
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Stealing credentials for further exploitation
Recommended Mitigation Strategies
To prevent and contain such incidents, the following actions are recommended:
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Isolate the Infected Host: Disconnect immediately to prevent further communication with the attacker’s infrastructure.
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Conduct a Forensic Analysis: Investigate the extent of the compromise, including additional payloads or backdoors.
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Review User Accounts: Reset passwords and revoke access if any credentials were compromised.
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Enhance Phishing Awareness: Conduct security training for employees to recognize phishing attempts.
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Implement Patch Management: Regularly update all software and operating systems to prevent exploits.
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Deploy Anti-Malware Solutions: Ensure robust endpoint protection is in place and actively monitored.
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Restrict Access Controls: Apply the principle of least privilege (PoLP) to limit download permissions.
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Improve Network Monitoring: Enhance security visibility to detect similar threats early.
References
VirusTotal Analysis of 188.124.9.56