Bastion hosts act as the only computer directly accessible from the public network to screen the private network from exposure. Firewalls defend internal network equipment from outside illegal access. Proxy servers act as intermediaries for client requests to other servers by evaluating requests, connecting to relevant servers, and optionally altering or caching responses. Search engines are tools that search the web and present search results to find information like web pages and data from databases or directories.

2. Bastion Host On the Internet, a bastion host is the only host computer that a company allows to be addressed directly from the ublic network and that is designed to screen the rest of its network from security exposure.

5. Search Engine A web search engine is a tool designed to search for information on the world wide web . The search results are usually presented in a list and are commonly called hits .The ingormation may consist of web pages , images also mine data available in databases or open directories .Unlike Web directories , which are maintained by human editors , search engines operate algorithmically or are a mixture of algorithmic and human input .