Review: Comodo Internet Security 4.0

Comodo Internet Security 4.0 secures your computer from Internet threats with a firewall, anti-virus protection and advanced intrusion prevention.

Comodo Internet Security secures your computer from Internet threats with a firewall, anti-virus protection and advanced intrusion prevention. CIS 4.0 is as simple or sophisticated to use as you want it to be.


  • Developer: Comodo
  • File size: 2.7MB for installer plus 132.3MB for livePCsupport, anti-virus and firewall installation files and anti-virus database.
  • Prerequisites: Internet Explorer 5.1 or higher. livePCsupport requires the livePCSupport option to be installed.
  • Hardware Requirements: 128MB available RAM and 210MB disk space
  • Operating system: 32 or 64-bit versions of Windows XP (SP2), Windows Vista or Windows 7
  • Price: Free
  • More Info: Comodo Home Page
  • Download: CIS 4.0 Download
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Who's it for?

CIS 4.0 is for anyone looking for a better firewall than Windows Firewall and additional security in one comprehensive software solution.

What problem does it solve?

CIS 4.0 provides functionality not found in Windows Firewall plus anti-virus protection and advanced threat detection not included with Windows but so essential for any computer connected to the Internet.

Standout features

  • Well organized GUI: The screens are organized into five categories:
    • Summary: CIS operational status, settings and user required actions
    • Antivirus: Eight common tasks for running scans, updating virus database, etc.
    • Firewall: Nine common and advanced firewall tasks
    • Defense+: Sixteen common, sandbox and advanced Defense+ tasks
    • More...: Seven additional tasks including access to the help file
  • Best of class firewall protection: Previous versions have been ranked among the best of any software based firewall to prevent both inbound and outbound threats according to and ConsumerSearch. CNET editors ranked CIS 3.14 five stars.
  • Simple to use settings: Simple slider-bars are used to configure user settings. They can be found at:
    • Antivirus | Scanner Settings
    • Firewall | Advanced | Firewall Behavior Settings
    • Defense+ | Sandbox | Sandbox Settings
    • Defense+ | Advanced | Image Execution Control Settings
    • Defense+ | Advanced | Defense+ Settings
    • The real-time virus scanner settings and the firewall settings can also be accessed from the Summary screen.
  • User customizable settings: Virtually all functionality can be customized to fit your personal needs.
  • Predefined firewall policies: Allows quick implementation of commonly used security policies.
  • Custom firewall policies: Advanced users can relatively easily create their own firewall policies.
  • Stealth mode: Hides your PC from port scans.
  • View active connections: Lists details of all active Internet connections.
  • Sandbox: Isolates unknown or non-trusted apps and reduces the risk of malicious behavior.
  • Fast Anti-virus scanning: A total scan of my system using default settings took only 20:05 minutes and scanned a total of 401,148 objects. (See What's wrong? below)
  • Real-time on demand virus protection: Applications are scanned on launch.
  • Manual and scheduled virus scanning: Perform scans manually and/or on a schedule. By default, full system anti-virus scanning is scheduled to run weekly.
  • Buffer Overflow Protection: Prevents malware from crashing the OS due to a buffer overflow attack.
  • Virus definition file available via download: It's not readily accessible but there is a way for users with a slow Internet connection to download the virus definition file.
  • Defense+ - Advanced intrusion detection incorporating white-listing, a Host Intrusion Protection System, and auto-sandboxing. Unknown or untrusted applications are automatically moved to the sandbox where they can be run with limited privileges, greatly reducing any potential damage.
  • Comodo Safe-List database: More than fifteen million safe applications are listed and allowed to run without user intervention.
  • Submit Suspicious Files: If you are suspicious of a file you can submit it to Comodo for analysis and possible inclusion in the Safe-List database.
  • Event Logging: Troubleshoot using logged activity generated events.
  • Diagnostics: If CIS is not performing properly you can run self-diagnostics to determine what is wrong.
  • Help File: The help file is hidden away under More... | Help but is excellent and very thorough with plenty of screenshots. I strongly recommend you browse through the help file if you have never used CIS. If you prefer, you can access the CIS Users Manual (6.9MB PDF) online.
  • Online help: The Get Live Support option available on most screens can be used for general questions but the wait times can be long. A livePCsupport subscription-based ID is required for other questions. You may be able to try livePCsupport free for 30 days by signing up for the free 30 day trial of Comodo Internet Security Pro 4.0, which includes livePCsupport.
  • Secure DNS service (optional): Uses a real-time block list to warn you of dangerous sites before you visit them. Comodo claims the service is a reliable, faster, smarter and safer Internet experience.
  • Threatcast Community (optional): Collects how you respond to alerts and gives you access to information how others responded in a bar chart format but I found a problem. (See What's wrong? below)
  • Freeware: CIS 4.0 is free for both personal and business use.

What's wrong?

  • Anti-Virus protection: The anti-virus scanner identified a number of possible threats not found in avast! that may be false positives. According to, Comodo scores comparability to other free anti-virus software like avast! and AVG.
  • Files greater than 20MB not scanned: By default, files larger than 20MB are not scanned when an anti-virus scan is performed. This can be modified by changing the numeric value in Antivirus | Scanner Settings | Real Time Scanning, Manual Scanning and Scheduled Scanning tabs Do not scan files larger than options. According to Comodo, only 0.00004% of known threats in their database are files larger than 20MB.
  • Possible problem scanning large compressed files: Raising the file size value to include larger files may cause the computer to lock up. Here are the test results:
  • Primary Computer (2GB)
    • Changed the Antivirus | Scanner Settings | Real Time Scanning, Manual Scanning and Scheduled Scanning tabs Do not scan files larger than options to 999999
    • Ran a scan of the Docs logical drive and the computer locked up.
  • Test Computer (4GB)
    • Changed the Antivirus | Scanner Settings | Real Time Scanning, Manual Scanning and Scheduled Scanning tabs Do not scan files larger than options to 999999 - ran a scan of the Docs logical drive and the scan completed successfully.
    • Removed 2GB of system memory - ran a scan of the Docs logical drive again and the computer locked up.
    • Reinstalled the 2GB of system memory - ran a scan of the Docs logical drive a third time and the scan completed successfully.
  • Threatcast tab missing: When an alert pops up the Threatcast tab is missing even if though I joined the Threatcast Community during installation.
  • Alerts: The Anti-virus, Firewall and Defense+ components use alerts to warn of a potentially harmful action. Users may not know when to accept or block the action though there is some guidance. The Threatcast Feature (optional) can be helpful to decide how to respond to an alert but it was missing.
  • Installer not Dial-up friendly: Downloading on dial-up at 31.2Kbps the installer failed with a timeout error but succeeded at 45.2Kbps. Downloading CIS 4.0 using the cisfree_installer.exe installer via dial-up is very difficult if not impossible. I can share several tips how it might be done if you but ask in the forum.
  • Installer does not support broken files: When the Internet connection is dropped the installer does not pick up where it left off but restarts the download of the file from the beginning. If the installer is restarted it will attempt to download all files whether they have been successfully downloaded previously or not.
  • Submission of all files in drive/folder fails: Selecting a folder in Antivirus | Submit Files fails with Compression error.
  • Limited language support: English, Russian and Chinese only. According to Comodo, more language support is coming soon.
  • Installing from the CIS_Setup.msi file does not incorporate anti-virus database: If you select Do not install the packages after download check box using the cisfree_installer.exe file, the virus definitions are not loaded or recognized.
  • Two EULAs: There are two different EULAs, one in the cisfree_installer.exe file and one in the CIS_Setup.msi file. The EULA found in the CIS_Setup.msi file is lengthy at 9,544 words. It includes a section that states that your usage may be tracked and reported but you cannot be personally identifiable.
  • livePCsupport Usage May Be Tracked and Reported: How you use livePCsupport may be tracked and sent to Comodo for analysis and for enforcement of the license agreement.
  • Toolbar: The Comodo HopSurf toolbar will be installed unless you opt-out when using the installer. When installing from the MSI file, the Comodo HopSurf toolbar will be installed and will become your default search provider unless you opt-out during installation.

Competitive products

Bottom line for business

Comodo Internet Security 4.0 offers one of the best firewalls available at any price. With the addition of anti-virus and Defense+ protection CIS 4.0 is a very good comprehensive solution for protection from Internet threats for both personal and business users alike.

User rating

Have you encountered or used Comodo Internet Security 4.0? If so, what do you think? Rate your experience and compare the results to what other TechRepublic members think. Give your own personal review in the TechRepublic Community Forums or let us know if you think we left anything out in our review.

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Author's Note

I would like to thank Comodo and Michael Kassner for spending more time helping with this review than I deserved.

After the superior performance I have experienced using the free Comodo Firewall I had high expectations for their free anti-virus software but am disappointed with some of the issues found with the anti-virus scanner. Here is where you can find information for the free Comodo Firewall if that is all you are looking for.

In Secure your computer after a Windows install or reinstall I describe how to block everything except the Windows Updater application. These instructions are slightly different in CIS 4.0 and the modified instructions can be found at Use Comodo Internet Security 4.0 to Lock Down Your PC Following a Windows Install or Reinstall.

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By Alan Norton

Alan Norton began using PCs in 1981, when they were called microcomputers. He has worked at companies like Hughes Aircraft and CSC, where he developed client/server-based applications. Alan is currently semi-retired and starting a new career as a wri...