When deciding to trust a macro-enabled Excel workbook (e.g., .xlsm files) downloaded from the Internet, several security considerations should be taken into account to minimize risks. Macro-enabled workbooks can contain executable code (VBA macros) that may pose significant security threats if malicious. Below is a concise breakdown of key considerations:

1. Source Reputation and Trustworthiness:

   • Verify the reputation of the repository owner. Check their profile for activity history, contributions, and community engagement. Well-known or verified contributors are generally more trustworthy.
     • A profile of the author/repository owner is published on LinkedIn
   • Review the repository's activity: Look at the number of stars, forks, and community engagement. A well-maintained repository with active issues and pull requests is less likely to host malicious code.
     • Excel to Graphviz Relationship Visualizer has published releases on SourceForge steadily since October 17, 2015.
       • It has a five star rating on SourceForge.
       • SourceForge has been awarded it a "Community Choice" badge, which is awarded to open source project that have reached the milestone of 10,000 total downloads.
   • Check for code reviews or comments in the repository. Contributions from multiple users or public discussions can indicate scrutiny and reliability.

2. Code Inspection:

   • Review the macro code before enabling it.
     • The VBA macro source code for the Excel to Graphviz Relationship Visualizer workbook is published online on GitHub here and can be viewed via a web browser before downloading or opening the workbook.
   • Open the workbook in a protected environment and inspect the VBA code (Alt+F11 in Excel). Look for suspicious actions like:
     • Network connections (e.g., accessing external URLs).
       • Excel to Graphviz Relationship Visualizer provides hyperlinks to external on-line help resources and on-line Graphviz graphing sites.
     • File system modifications (e.g., creating, deleting, or altering files).
       • Excel to Graphviz Relationship Visualizer creates text and image files.
     • Execution of external programs or scripts.
       • Excel to Graphviz Relationship Visualizer executes the Graphviz dot command-line program to convert dot source files into rendered graphs.
   • If you lack VBA expertise, consider using online tools or sandboxes to analyze the code for malicious behavior.
     • Macros in the Excel to Graphviz Relationship Visualizer workbook undergo static code analysis via RubberduckVBA before publication. It provides a suite of tools and features aimed at improving code quality, maintainability, and testing in VBA projects.

3. File Verification:

   • Scan the file with antivirus software before opening it. Use reputable antivirus tools or online scanners like VirusTotal to detect known malware signatures.

     • Official releases of the Excel to Graphviz Relationship Visualizer workbook are published on SourceForge at https://sourceforge.net/projects/relationship-visualizer/.
     • SourceForge automatically scans all uploaded files for viruses at the time of upload.
     • Files uploaded to SourceForge are only made available for download after passing a successful virus scan.
     • Avoid files from unauthorized mirrors, repackaged distributions, or files you didn't download directly as these may compromise integrity or security.

   • Check the file's integrity by verifying its hash if provided by the repository. This ensures the file hasn't been tampered with.

     • The Excel to Graphviz Relationship Visualizer download files, along with their SHA1 and MD5 hashes, are published on the Files tab on SourceForge.
     • If you don’t see them, click the circle (i) icon on the right side of the screen to reveal file details.

   • When you download an executable file on Windows, you may need to uncheck the "Unblock" property to allow the program to run. This is because Windows often marks downloaded files as potentially unsafe, adding a block that prevents execution until you explicitly allow it. Macro-enabled Excel workbooks fall into this category.

     To unblock a file, do this:

     1. Right-click the downloaded executable file.
     2. Select Properties.
     3. In the General tab, look for a checkbox labeled "Unblock" near the bottom (it appears if the file is marked as blocked).
     4. Check the Unblock box (or uncheck it if it's already checked, depending on the system's phrasing, but typically you check it to unblock).
     5. Click OK or Apply.

     This removes the security restriction, allowing the program to run. If you don’t see the "Unblock" option, the file may not be blocked, or you might need to adjust other security settings, like running as administrator or checking antivirus restrictions.

4. Excel Security Settings:

   • Ensure Excel's macro settings are configured to disable macros by default with a prompt to enable them (found in Trust Center > Macro Settings). This prevents macros from running automatically.
   • Avoid enabling macros unless you've thoroughly vetted the file. If prompted to enable macros upon opening, proceed cautiously.

5. Isolated Environment:

   • Open the workbook in a sandboxed or isolated environment, such as a virtual machine (VM) or a dedicated device not connected to sensitive networks or data. This limits potential damage if the macro is malicious.
   • Alternatively, use a cloud-based or disposable environment (e.g., Windows Sandbox) to test the file.

6. Purpose and Necessity:

   • Evaluate whether the workbook's functionality requires macros. If the workbook's purpose can be achieved without enabling macros, avoid enabling them.
     • The Excel to Graphviz Relationship Visualizer workbook is entirely dependent upon enabled macros.
     • If you cannot enable macros, you cannot use the software.
   • Check if the repository provides documentation explaining the macro's purpose and functionality. Lack of clear documentation is a red flag.
     • The Excel to Graphviz Relationship Visualizer source code is fully documented, however there are thousands of lines of macro-code in its codebase, and comments are geared for maintenance and support.
     • Robust end-user documentation is published on https://exceltographviz.com.

7. Community Feedback and Reports:

   • Search for user feedback in the repository's issues, discussions, or related X / Twitter posts. Look for reports of suspicious behavior or security concerns.
     • SourceForge -> Support Tickets
     • GitHub -> Issues.
     • X / Twitter -> @ExcelToGraphviz
   • Check external sources (e.g., forums, blogs) for reviews or warnings about the workbook or its creator.

8. Update and Maintenance:

   • Confirm the repository is actively maintained. Abandoned projects or outdated files may contain unpatched vulnerabilities.
     • Excel to Graphviz Relationship Visualizer has steadily published
       • Downloadable run-time files on SourceForge since October 17, 2015.
       • Exported VBA code, and web-site markdown content on GitHub since February 11, 2022.
   • Look for recent commits or updates addressing security concerns.

9. Alternative Options:

   • Consider whether a non-macro-enabled version or alternative tool exists that meets your needs without the risks associated with macros.
   • Explore trusted, well-known libraries or tools instead of obscure SourceForge/GitHub downloads.

• Download cautiously: Only download from the official repository link, not third-party mirrors or unverified sources.
• Backup data: Ensure critical data is backed up before opening the workbook to mitigate potential damage.
• Limit permissions: Run Excel with minimal permissions (e.g., as a standard user, not an administrator) to reduce the impact of malicious code.

• Lack of documentation or unclear macro purpose.
• Requests for unusual permissions or external connections.
• Poorly rated or unverified repository with minimal activity.
• Warnings from antivirus software or community reports.

By combining these considerations-verifying the source, inspecting code, using secure environments, and staying cautious-you can make an informed decision about trusting a macro-enabled Excel workbook from SourceForge/GitHub. If in doubt, consult a cybersecurity expert or avoid enabling macros altogether.