0.0 Executive Summary
This report documents the development and implementation of a Python-based algorithm used to manage IP address allow lists.
The objective was to reduce the risk of unauthorized access and manual configuration errors by automating allow list updates through a controlled script.
The result is a more reliable and auditable process that replaces manual updates with an automated approach that keeps system access lists accurate and up to date.
1.0 Python Algorithm for Managing IP Access
1.1 Project Description
The goal of this task was to build a dynamic allow list management system to control which IP addresses can access protected resources.
Python was used to:
- Automate the parsing and updating of allow and remove lists
- Remove unauthorized or outdated IP addresses from the allow list
- Maintain an accurate record of valid IPs using file-based storage
This approach helps ensure that only approved IP addresses remain authorized, reducing the risk of unauthorized access.
1.2 Technical Task / Troubleshooting Process
The process focused on replacing manual allow list updates with a script-based approach to improve accuracy and consistency.
Key Actions & Observations
-
Reviewed the allow list file (
allow_list.txt) and identified outdated or unnecessary IP entries. -
Implemented file handling using the
with open()context manager to ensure safe file operations. -
Converted file contents into a list using
.split()for easier processing. -
Used conditional logic to compare entries against a remove list and eliminate unauthorized IPs.
-
Reconstructed the updated allow list using
.join()and wrote it back to the file. -
Ensured proper handling of formatting, including whitespace and newline characters.
-
Verified that the final output matched the intended access policy.
-
Documented the script logic to support reuse and future automation efforts.
Root Cause: Manual updates to allow lists can lead to outdated entries remaining in place. This creates “permission creep,” where unnecessary IPs retain access. This was resolved by automating the process with a repeatable Python script that enforces consistent updates.
1.3 Resolution and Validation
The access control process was secured by applying and validating the automated script.
| Parameter | Configuration Value |
|---|---|
| Management Tool | Python 3.x |
| Control State | Automated |
| Security Mode | Dynamic Allow List Enforcement |
| Scope | Network Access Control Files |
Validation Steps
-
Executed the script on an allow list containing over 100 IP addresses with a defined remove list.
-
Confirmed that the specified IPs were successfully removed without affecting valid entries.
-
Verified that the output file maintained correct formatting and could be used by dependent systems such as firewalls or web servers.
2.0: CONCLUSION
2.1 Key Takeaways
- Manual allow list management is error-prone and does not scale effectively.
- Automating access control reduces human error and improves consistency.
- Testing is required to ensure that list operations handle edge cases correctly, such as missing or duplicate entries.
- Automated updates allow access control policies to stay aligned with user and system changes.
2.2 Security Implications & Recommendations
Risk: Stale or Orphaned IP Entries
Old IP addresses left in allow lists may provide unintended access.
Mitigation: Automate allow list updates and regularly validate entries.
Risk: File Write Errors
Improper file handling can corrupt the allow list or cause data loss.
Mitigation: Use safe file handling practices such as the with open() context manager to ensure proper file closure.
Best Practices
- Apply least privilege by removing access immediately when it is no longer required
- Schedule the script to run automatically using tools such as Cron or Task Scheduler
- Validate outputs after each run to ensure no critical IPs are removed unintentionally
- Maintain documentation of the script and its logic for auditing and troubleshooting
Framework Alignment
- Aligns with NIST SP 800-53 (AC-2 Account Management) for managing access permissions
- Supports ISO 27001 (A.9.2.2) for user access provisioning and de-provisioning
- Aligns with the NIST CSF Protect function by enforcing automated access control mechanisms