A cybersecurity team deploys an Intrusion Prevention System (IPS) to enhance their threat prevention capabilities. Soon after deployment, they notice that legitimate traffic is being blocked. What is the most likely cause of this issue?

An Intrusion Prevention System (IPS) inspects network traffic against a set of predefined signatures or rules to identify malicious activity. When these rules are "overly strict" or too broad, they can incorrectly match patterns found in legitimate, benign traffic. This event is known as a "false positive." The IPS, functioning as designed, then blocks this misidentified traffic. This is a common challenge immediately following an IPS deployment and requires a period of "tuning" to adjust the rule-set to the specific network's traffic patterns, thereby reducing false positives.

A. Incorrect user access permissions: User access permissions are typically enforced by identity management systems or operating systems, not by the traffic pattern analysis function of an IPS.
C. Firewall misconfigurations: While a firewall misconfiguration can block legitimate traffic, the question specifies the issue occurred after deploying an IPS, making the IPS's own rules the most direct and probable cause.
D. Lack of encryption on the network: Lack of encryption is a vulnerability. An IPS blocks traffic based on malicious signatures within the content, not typically on the absence of encryption itself. ---

1. Vendor Documentation:

Cisco, "Intrusion Prevention System (IPS) Tuning," Document ID: 118947. The document states, "A false positive is an event that is flagged by a signature, but is not malicious... The goal of tuning is to eliminate false positives." This directly links overly sensitive signatures to the blocking of legitimate traffic.

2. University Courseware:

Stanford University, CS 155: Computer and Network Security, Lecture 13: "Network Security & Firewalls." The course notes discuss Intrusion Detection Systems (the detection component of an IPS) and the fundamental problem of false positives, where "benign activity [is] mistakenly flagged as malicious" due to the nature of the detection signatures.

3. Peer-Reviewed Academic Publication:

Liao, H. J., Lin, C. H. R., Lin, Y. C., & Tung, K. Y. (2013). "Intrusion detection system: A comprehensive review." Journal of Network and Computer Applications, 36(1), 16-24. Section 2.1, "Signature-based Detection," explains that this method can "produce false alarms if the signatures are not defined well to match only the malicious traffic." (DOI: https://doi.org/10.1016/j.jnca.2012.09.004)