A proxy server acts as an intermediary between clients and servers, forwarding requests on behalf of clients and returning responses. From the destination server’s perspective, the request comes from the proxy, not the original client. This provides privacy, enables content filtering, and allows inspection of traffic.
Forward proxies serve clients connecting to external resources — an organization’s web proxy filters employee internet access, logs browsing activity, and blocks malicious sites. Reverse proxies protect servers by sitting in front of them and handling incoming requests — web application firewalls often function as reverse proxies that inspect and filter traffic before it reaches application servers.
CISSP Relevance
Proxy servers are addressed in Domain 4 (Communications and Network Security). CISSP candidates must understand both forward and reverse proxy architectures, how proxies support security monitoring and policy enforcement, and how SSL/TLS inspection through proxies introduces both security capabilities and privacy considerations.
External reference: NIST Glossary Proxy Server
Related terms: Firewall, Network Segmentation