Network sniffing tools and packet analyser tools are generally the same thing, the main purpose of sniffing is to analyse the incoming and outgoing packets, keep in mind when you connect to a web server or to any network (computer) you sends your data via wired connection or wireless connection in the form of packets, your data goes in the form of packets.


A packet contain the source (Sender) and the destination (Receiver) IP and MAC address and also it contains the data that are going to be sent. So just imagine if someone get this packet than he/she can easily know what you have send, an attacker can easily sniff your confidential information (credit card, paypal, passwords etc), so the sniffing is the important attack that should be consider as a security measure.


Large organisation and web server uses secure connection for transmission for example paypal uses https:// instead of http:// so its means your data goes in the form of encrypt data. To learn more about SSL (secure socket layer) click here. If you are using SSL it does not mean that you are secure ever there is way to crack the secure channel click here to learn with backtrack5.


All the thing that discussed above shows that sniffing is not a good thing, however it is not true the Positive usage of sniffer is also its regular usage, which aim is to maintain network and system working normally.

• Capturing packets
• Recording and analysing traffic
• Decrypting packets and displaying in clear text
• Converting data to readable format
• Showing relevant information like IP, protocol, host or server name and so on.

While the negative usage is open and clear:

• Catching password, which is the main reason for most illegal uses of sniffing tool
• Capturing special and private information of transactions, like username, credit ID, account, and password
• Recording email or instant message and resuming its content
  

The famous and the most widely used tools for sniffing purposes are:

• Wireshark (We will discuss it on later)
• Kismet   (For wireless sniffing, discussed)
• Netstumber (For wireless sniffing, discussed)
• Kismac (For Wireless sniffing, discussed)
• Ettercap (We will discuss it on later)
• Tcpdump ( We will discuss it on later)
• Cain and Abel ( We will discuss it on later)
• Etc