requests and send them to a proxy server. While being more complex to set up, this option
avoids any configuration changes on the user’s computer.
Figure 3.5 shows how HTTP proxy filtering is applied. The ISP structure is different from figure 3.1 because the proxy server must intercept all requests. This gives it the opportunity of
seeing both the Web site domain name and which page is requested, allowing more precise
blocking when compared to TCP/IP header or DNS filtering.
Hybrid TCP/IP and HTTP Proxy
As the requests intercepted by an HTTP proxy must be reassembled from the original packets, decoded, and then retransmitted, the hardware required to keep up with a fast Internet
connection is very expensive. So systems like the BT Cleanfeed project
3 were created, which
give the versatility of HTTP proxy filtering at a lower cost. It operates by building a list of the IP
addresses of sites hosting prohibited content, but rather than blocking data flowing to these
Figure 3.5
HTTP proxy blocking.
Tools and Technology of Internet Filtering
63
avoids any configuration changes on the user’s computer.
Figure 3.5 shows how HTTP proxy filtering is applied. The ISP structure is different from figure 3.1 because the proxy server must intercept all requests. This gives it the opportunity of
seeing both the Web site domain name and which page is requested, allowing more precise
blocking when compared to TCP/IP header or DNS filtering.
Hybrid TCP/IP and HTTP Proxy
As the requests intercepted by an HTTP proxy must be reassembled from the original packets, decoded, and then retransmitted, the hardware required to keep up with a fast Internet
connection is very expensive. So systems like the BT Cleanfeed project
3 were created, which
give the versatility of HTTP proxy filtering at a lower cost. It operates by building a list of the IP
addresses of sites hosting prohibited content, but rather than blocking data flowing to these
Figure 3.5
HTTP proxy blocking.
Tools and Technology of Internet Filtering
63