The security engineer is likely to deploy a Web Application Firewall (WAF) to protect the new web portal service. A WAF specifically protects web applications by filtering, monitoring, and blocking HTTP requests based on a set of rules. This is crucial for preventing common attacks such as SQL injection, cross-site scripting (XSS), and other web-based attacks that could compromise the web service.

Layer 4 firewall operates primarily at the transport layer, focusing on IP address and port filtering, making it unsuitable for web application-specific threats.

NGFW (Next-Generation Firewall) provides more advanced filtering than traditional firewalls, including layer 7 inspection, but the WAF is tailored specifically for web traffic.

UTM (Unified Threat Management) offers a suite of security tools in one package (like antivirus, firewall, and content filtering), but for web application-specific protection, a WAF is the best fit​​​.