When dealing with suspected malicious activity involving obfuscated PowerShell scripts-especially when launched from Microsoft Word documents-behavioral analysis is the most critical next step. This approach helps in determining if the process chain is part of a known attack pattern, such as a phishing attempt using malicious macros that launch PowerShell for data exfiltration or payload download.
As highlighted in the CyberOps Technologies (CBRFIR) 300-215 study guide, understanding behavior and deobfuscating PowerShell scripts is an essential part of the forensic and incident response process.
Specifically:
* During the detection and analysis phase, if PowerShell is used with obfuscated or encoded commands, responders should investigate the intent and behavior of the command.
* Deobfuscation allows analysts to see what the script is doing (e.g., downloading files, creating persistence mechanisms, or opening a reverse shell).
The guide states:
"For example, if the threat is malware, the compromised system should be immediately isolated and the malware should be placed in a sandbox or a detonation chamber to understand what it is trying to do".
This confirms that understanding execution behavior (such as what the PowerShell script intends to perform) is key to uncovering indicators of compromise (IoCs).
Thus, option C-conducting a behavioral analysis and deobfuscating PowerShell-is the most critical and effective response at this stage.

Theroot cause analysisin incident response focuses on identifying theinitial trigger or root causeof the incident to understand how it started and how to prevent recurrence. In this scenario, thephishing email sent to the victim(A) is the initial trigger that led to the employee's action of clicking the malvertising link, resulting in the malware download.
The other options represent later stages in the incident response cycle, such as detection (SIEM alert, cybersecurity team's alert) or supporting evidence (email header information), but they do not address the root cause, which is thephishing email itself.
This aligns with theCyberOps Technologies (CBRFIR) 300-215 study guide, which states that identifying theinitial vector of compromiseis critical to theroot cause analysisphase of incident response (Chapter:
Incident Response Techniques, page 410-412).
Reference:CyberOps Technologies (CBRFIR) 300-215 study guide, Chapter: Incident Response Techniques, Root Cause Analysis, page 410-412.

According to the Cisco CyberOps Associate guide, the goal of a root cause analysis is to determine how an attacker successfully exploited a system so that similar vulnerabilities can be mitigated in the future. The
"method of infection" (e.g., phishing email with malicious attachment, drive-by download, credential compromise, etc.) is the most relevant factor in understanding the initial access vector and subsequent spread of ransomware across the network.
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The Wireshark output shows SMB protocol transactions, including NT Create AndX Response and Write AndX Response, indicating the transfer of files or objects. SMB (Server Message Block) is a protocol used for file sharing and printer access in Windows networks. The log does not indicate phishing or redirection behavior but rather normal SMB communication such as accessing files or shared resources.
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* TCPdumpis a CLI-based packet capture tool that is widely used for real-time traffic inspection and analysis on Unix/Linux systems.
* TCPsharkis a variant CLI tool used similarly for packet analysis.
AlthoughWiresharkis a powerful network protocol analyzer, it requires a GUI. Therefore, it is not suitable for environments without a graphical interface.