Misconfigured ACLs
TLDR: Misconfigured ACLs (Access Control Lists) can lead to unintended security risks and network functionality issues. Errors such as overly permissive rules, incorrect ordering, or failure to specify deny rules properly may allow unauthorized access or block legitimate traffic. These mistakes compromise the intended role of ACLs in filtering traffic and enforcing security policies, potentially exposing the network to data breaches or DDoS attacks.
https://en.wikipedia.org/wiki/Access_control_list
One major cause of ACL misconfiguration is the lack of granularity in rules. For example, applying a blanket rule to permit all traffic from a certain IP range without specific restrictions can inadvertently allow malicious activity. Additionally, improperly ordered ACL entries can result in unintended matches, as ACLs are processed in a top-down manner. This can lead to early termination of rule evaluation, bypassing crucial security checks or creating performance bottlenecks due to inefficient filtering.
To avoid misconfigured ACLs, administrators should follow best practices such as using explicit deny rules, maintaining a least-privilege approach, and documenting ACL policies thoroughly. Regular audits and testing tools like Cisco Packet Tracer or Wireshark can identify gaps and ensure configurations meet the intended security posture. Additionally, segmenting ACLs based on functionality and applying them to specific interfaces or traffic types improves clarity and reduces the risk of misconfiguration.
https://www.cisco.com/c/en/us/td/docs/ios/tools/command/reference/itr_book.html