The analysis of scan data against the hardening guidelines reveals non-compliance in AppServ2 and AppServ3.

• AppServ2 is running Apache version 2.3.48, which is below the required version 2.4.18 or greater. Additionally, its Nmap scan shows only port 80 (HTTP) is open, meaning it is not using the default port 443 for a secure service (HTTPS).
• AppServ3 has an open HTTPS port (443), but the ssl-enum-ciphers scan fails to report that TLS 1.2 is enabled, which violates the guideline requiring TLS 1.2 as the only active version.
• AppServ1 and AppServ4 are considered compliant as the provided data does not indicate any violations of the specified hardening guidelines.

National Institute of Standards and Technology (NIST). (2019). Special Publication 800-52r2: Guidelines for the Selection, Configuration, and Use of Transport Layer Security (TLS) Implementations. Section 3.1 recommends that "servers that support government-only applications and clients shall be configured to use TLS 1.2 and should be configured to use TLS 1.3." The absence of a confirmed TLS 1.2 configuration on AppServ3 makes it non-compliant. https://doi.org/10.6028/NIST.SP.800-52r2

The Apache Software Foundation. Apache HTTP Server 2.4 documentation. The official Apache documentation outlines features and security fixes introduced in new versions. Using an outdated version like 2.3.48 (as seen on AppServ2) means missing critical security patches and features available in the required 2.4.18 and later versions.

Nmap.org. Nmap Scripting Engine (NSE) Documentation: ssl-enum-ciphers. The official Nmap documentation explains that this script queries a server to enumerate its supported SSL/TLS protocol versions and ciphers. The lack of output for AppServ3 indicates a configuration issue, while the specific output for AppServ4 confirms its use of TLS 1.2.

Internet Engineering Task Force (IETF). (2008). RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2. Section F.1.1 describes version negotiation. If a server cannot negotiate a compliant version (TLS 1.2), it violates protocols designed to ensure secure communication.