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Difficulty: MediumWeb Browser Security and Pop-Up/Redirect Troubleshooting

A help desk technician receives a call from an employee who cannot access a secure corporate intranet application. When the employee navigates to the application URL, the web browser displays a security warning stating that the SSL/TLS certificate name does not match the requested domain name (NET::ERR_CERT_COMMON_NAME_INVALID). Other users on the same subnet can access the internal site without any certificate errors. Which of the following should the technician check FIRST on the affected computer?

  1. The local hosts file for unauthorized static domain IP mappingsAnswer
  2. B
    The browser's site permissions and pop-up blocker exceptions
  3. C
    The default home page setting in the browser configuration
  4. D
    The Windows Credential Manager for expired network credentials

Answer

The technician should first inspect the local hosts file for unauthorized static domain IP mappings.
Inspecting the local hosts file is the correct initial step because static entries in C:\Windows\System32\drivers\etc\hosts override DNS queries. When a single workstation experiences a certificate domain mismatch for a site that works for all other users, an incorrect IP mapping in the hosts file redirects traffic to an unexpected web server presenting a different SSL certificate.

Step-by-Step Solution

1
Analyze the reported browser symptom and scoping details.
The issue is isolated to a single computer receiving a certificate common name mismatch error for an internal URL.
Because other users on the same subnet access the site normally, the issue resides locally on the specific workstation rather than on the server or network infrastructure.
2
Identify potential local name resolution tampering mechanisms.
The local Windows hosts file (C:\Windows\System32\drivers\etc\hosts) overrides DNS resolution for specific hostname entries.
If malicious software or improper configuration modified the hosts file, the domain name resolves to an incorrect destination server, triggering an SSL/TLS common name mismatch warning.
3
Determine the appropriate troubleshooting priority step.
Inspecting and restoring the local hosts file directly targets the root cause of single-host domain redirection.
Clearing cache or altering browser GUI preferences will not rectify localized static DNS hijack entries.

Key Concept

Host File Redirection and Name Resolution Troubleshooting
Estimated Time:1m 0s
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Topics

Web Browser Security and Pop-Up/Redirect Troubleshooting

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