Network sniffing

Network sniffing is scanning the communication on a network for either diagnostic or malicious reasons. Benign cases are also known as Network monitoring; malicious cases are more likely called Packet sniffing

Example
To get to know your HTTP Server a bit better, you could use netcat: bob:~ # netcat localhost 80 GET /index.htm HTTP/1.1 User-Agent: Mozilla/5.0 (compatible; Konqueror/3.5; Linux) KHTML/3.5.7 (like Gecko) Accept: text/html, image/jpeg, image/png, text/*, image/*, */* Accept-Encoding: x-gzip, x-deflate, gzip, deflate Accept-Charset: utf-8, utf-8;q=0.5, *;q=0.5 Accept-Language: en Host: localhost:8000 Connection: Keep-Alive

HTTP/1.1 200 OK Date: Sun, 15 Jul 2007 23:38:10 GMT Server: Apache/2.2.3 (Linux/SUSE) Last-Modified: Sun, 15 Jul 2007 23:12:19 GMT ETag: "28c014-6-79cfdac0" Accept-Ranges: bytes Content-Length: 6 Keep-Alive: timeout=15, max=100 Connection: Keep-Alive Content-Type: text/html

hallo bob:~ #

Or for example if you want to know what mediawiki sends to the server, you point your browser to mediawiki, stop apache, start netcat -l -p 80 and change a page in mediawiki.