Turning off the machine is the first and most urgent step to prevent further damage to the host and other systems. Ransomware can encrypt files, steal data, and spread to other devices on the network if the infected machine remains online. Turning off the machine will stop the ransomware process and isolate the machine from the network12. The other options are either ineffective or risky. Running a full antivirus scan may not detect or remove the ransomware, especially if it is a new or unknown variant. Removing the LAN card may disconnect the machine from the network, but it will not stop the ransomware from encrypting or deleting files on the local drive. Installing a different endpoint solution may not be possible or helpful if the ransomware has already compromised the system or blocked the installation.

Explanation
Account lockout would best mitigate the threat of a dictionary attack

Explanation
Account lockout would best mitigate the threat of a dictionary attack1

A possible cause of the user being redirected to unexpected websites is that the localhost file entries have been modified by malware or hackers to point to malicious or unwanted websites. The localhost file is a text file that maps hostnames to IP addresses and can override DNS settings. By examining the localhost file entries, a technician can identify and remove any suspicious or unauthorized entries that may cause the redirection issue. Enabling firewall ACLs may not resolve the issue if the firewall rules do not block the malicious or unwanted websites. Verifying the routing tables may not resolve the issue if the routing configuration is correct and does not affect the web traffic. Updating the antivirus definitions may help prevent future infections but may not remove the existing malware or changes to the localhost file. Reference: CompTIA A+ Core 2 (220-1002) Certification Exam Objectives Version 4.0, Domain 1.3

The error message "Your connection is not private. Authority invalid." means that the web browser cannot verify the identity or security of the website's SSL certificate. This could indicate that the website has been compromised, has a configuration error, or has an expired or invalid certificate. The user should not proceed to the site or use a different browser, as this could expose their sensitive information to potential attackers. The user should also not reinstall the browser, as this is unlikely to fix the error and could cause data loss. The best action for the user to take is to report the error to the bank and wait for them to resolve it.
References: : How to Fix "Your Connection Is Not Private" Errors
(https://www.howtogeek.com/874436/how-to-fix-your-connection-is-not-private-errors/) : Fix connection errors (https://support.google.com/chrome/answer/6098869?hl=en)