The eradication phase in incident response involveseliminating the root cause of the incidentand strengthening defenses to prevent reoccurrence. In this case:

Intrusion Prevention System (D): Adding new rules to the IPS to detect and block malicious activity on TCP/135 is a direct eradication step to remove the threat’s entry point and prevent future attacks.

Centralized User Management (C): Hardening user accounts, removing unnecessary permissions, and applying tighter authentication/authorization measures helps eliminate the possibility that threat actors could exploit weak or mismanaged accounts to continue accessing the system.

Althoughanti-malware software (A)andenterprise block listing (E)are valuable, themost direct eradication stepshere specifically involve managing network access (via IPS) and strengthening user controls (via centralized user management), especially when TCP/135 (MSRPC endpoint mapper) can be used to enumerate services and potentially access vulnerable endpoints remotely.

This aligns with best practices outlined in incident response frameworks (such as the NIST SP 800-61 and referenced resources), which emphasizeclosing the exploited entry points(in this case, TCP/135) andremoving any lingering access pointsthrough user management and network control enhancements.

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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Volatility is an open-source memory forensics tool specifically designed for memory analysis. It allows forensic investigators to inspect memory dumps for running processes, hidden processes, injected code, and malicious activity in memory.

As per the Cisco CyberOps Associate study guide, “Volatility helps security professionals with both incident response and malware analysis. It can identify processes, registry artifacts, network connections, and memory-resident malware”.

While Memoryze (D) is also a memory analysis tool, Volatility is the more recognized, command-line driven tool used widely in industry and is directly highlighted in the curriculum.

According to theCyberOps Technologies (CBRFIR) 300-215 study guidecurriculum, when analyzing suspicious behavior—especially when scripts or shell commands are executed from applications like Word (which is uncommon)—the encoded PowerShell payload must be decoded to determine if malicious intent is present. Deobfuscation is a critical step in identifying command-and-control behavior, persistence, or malware execution paths.

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The Cisco study material recommends integrating automation for log/event collection and contextual analysis to reduce detection delays and ensure rapid identification of anomalies. It also emphasizes the need for pre-defined roles and documented steps in anIncident Handling Playbook, following NIST SP 800-61 Rev.2 standards, to improve consistency and readiness during incidents.

Comprehensive and Detailed Explanation:

The log entries show repeated SSH login attempts for various invalid usernames (e.g., admin, phoenix, rainbow, test, user, etc.) from different source ports. These are clear signs of a brute-force attack—an automated process trying multiple usernames and passwords in hopes of gaining access.

Mitigating such attacks includes:

Implementing account lockout policies (e.g., locking an account after several failed login attempts).

Enabling Multi-Factor Authentication (MFA) to ensure that password guessing alone is insufficient for account access.

Therefore, the correct answer is:

D. Brute-force attack; implement account lockout policies and roll out MFA.