Secure proxies are also used for screening purposes. This allows the administrator to contain access to undesirable or unwanted sites. Besides, secure proxy servers are also used for caching purposes, enabling faster access to frequently used sites.
These types of proxies work on the application layer – the seventh layer of the OSI model. Unlike firewalls which work differently on lower layers, secure proxies tend to stay application dependent.
These types of proxies aren’t easy to install and are highly difficult than firewalls simply because the functionality for every protocol application is configured one at a time.
Nevertheless, well-configured secure proxies enhance performance and security. With proxy servers functioning at OSI application layer, the filtering applications are very sharp. By inspecting messages, proxy web servers easily check URL addresses of outgoing web page requests.
Message function allows network administrators to bar access to few sites and permit access to others. Normal firewalls hardly check web domain names within messages.
The same way, for incoming data, ordinary routers filter by network address or port number. However, proxy servers also filter based on application content within the messages.