To ensure the most secure way of keeping a legacy system (COL) operating until a new solution is available, isolating the system and enforcing strict firewall rules is the best approach. This method minimizes the attack surface by restricting access to only the necessary endpoints, thereby reducing the risk of unauthorized access and potential security breaches. Isolating the system ensures that it is not exposed to the broader network, while firewall rules control the traffic that can reach the system, providing a secure environment until a replacement is implemented.
References:
* CompTIA SecurityX Study Guide: Recommends network isolation and firewall rules as effective measures for securing legacy systems.
* NIST Special Publication 800-82, "Guide to Industrial Control Systems (ICS) Security": Advises on isolating critical systems and using firewalls to control access.
* "Network Security Assessment" by Chris McNab: Discusses techniques for isolating systems and enforcing firewall rules to protect vulnerable or legacy systems.
By isolating the system and implementing strict firewall controls, the organization can maintain the necessary operations securely while working on deploying a new solution.

The log-in activity indicates a security threat, particularly involving the ADMIN account with a high-risk failure status. This suggests that the account may be targeted by malicious activities such as credential stuffing or brute force attacks.
* Updating log configuration settings (A) may help in better logging future activities but does not
* address the immediate threat.
* Changing the admin account password (B) is a good practice but may not fully mitigate the ongoing threat if the account has already been compromised.
* Blocking employees (C) from logging into non-business applications might help in reducing attack surfaces but doesn't directly address the compromised account issue.
Implementing automation to disable accounts associated with high-risk activities ensures an immediate response to the detected threat, preventing further unauthorized access and allowing time for thorough investigation and remediation.
References:
* CompTIA SecurityX guide on incident response and account management.
* Best practices for handling compromised accounts.
* Automation tools and techniques for security operations centers (SOCs).

Based on the provided authentication logs, we observe that User1's account experienced multiple failed login attempts within a very short time span (at 8:01:23 AM on 12/15). This pattern indicates a potential brute-force attack or an attempt to gain unauthorized access. Here's a breakdown of why disabling User1's account is the appropriate first step:
* Failed Login Attempts: The logs show that User1 had four consecutive failed login attempts:
* VM01 at 8:01:23 AM
* VM08 at 8:01:23 AM
* VM01 at 8:01:23 AM
* VM08 at 8:01:23 AM
* Security Protocols and Best Practices: According to CompTIA Security+ guidelines, multiple failed login attempts within a short timeframe should trigger an immediate response to prevent further potential unauthorized access attempts. This typically involves temporarily disabling the account to stop ongoing brute-force attacks.
* Account Lockout Policy: Implementing an account lockout policy is a standard practice to thwart brute-force attacks. Disabling User1's account will align with these best practices and prevent further failed attempts, which might lead to successful unauthorized access if not addressed.
* References:
* CompTIA Security+ SY0-601 Study Guide by Mike Chapple and David Seidl
* CompTIA Security+ Certification Exam Objectives
* NIST Special Publication 800-63B: Digital Identity Guidelines
By addressing User1's account first, we effectively mitigate the immediate threat of a brute-force attack, ensuring that further investigation can be conducted without the risk of unauthorized access continuing during the investigation period.