Ethical Hacking - Sniffing
Sniffing is a process of monitoring and capturing all data packets passing through given network. Sniffers are used by network/system administrator to monitor and troubleshoot network traffic. Attackers use sniffers to capture data packets containing sensitive information such as password, account information etc. Sniffers can be hardware or software installed in the system. By placing a packet sniffer on a network in promiscuous mode, a malicious intruder can capture and analyze all of the network traffic.
Types of Sniffing
- Passive Sniffing - This is the process of sniffing through the hub. Any traffic that is passing through the non-switched or unbridged network segment can be seen by all machines on that segment. Sniffers operate at the data link layer of the network. Any data sent across the LAN is actually sent to each and every machine connected to the LAN. This is called passive since sniffers placed by the attackers passively wait for the data to be sent and capture them.
- Active Sniffing - Sniffing in the switch is active sniffing. A switch is a point to point network device. The switch regulates the flow of data between its ports by actively monitoring the MAC address on each port, which helps it pass data only to its intended target. In order to capture the traffic between target sniffers has to actively inject traffic into the LAN to enable sniffing of the traffic. This can be done in various ways.
Active Sniffing Techniques
- MAC Flooding.
- DHCP Attacks
- DNS Poisoning
- Spoofing Attacks
- ARP Poisoning
Protocols which are affected in sniffing technique
Protocols such as the tried and true TCP/IP were never designed with security in mind and therefore do not offer much resistance to potential intruders. Several rules lend themselves to easy sniffing.
- HTTP − It is used to send information in the clear text without any encryption and thus a real target.
- SMTP (Simple Mail Transfer Protocol) − SMTP is basically utilized in the transfer of emails. This protocol is efficient, but it does not include any protection against sniffing.
- NNTP (Network News Transfer Protocol) − It is used for all types of communications, but its main drawback is that data and even passwords are sent over the network as clear text.
- POP (Post Office Protocol) − POP is strictly used to receive emails from the servers. This protocol does not include protection against sniffing because it can be trapped.
- FTP (File Transfer Protocol) − FTP is used to send and receive files, but it does not offer any security features. All the data is sent as clear text that can be easily sniffed.
- IMAP (Internet Message Access Protocol) − IMAP is same as SMTP in its functions, but it is highly vulnerable to sniffing.
- Telnet − Telnet sends everything (usernames, passwords, keystrokes) over the network as clear text and hence, it can be easily sniffed.
Sniffers are not the dumb utilities that allow you to view only live traffic. If you really want to analyze each packet, save the capture and review it whenever time allows.
Hardware Protocol Analyzers
- Before we go into further details of sniffers, it is important that we discuss about hardware protocol analyzers. These devices plug into the network at the hardware level and can monitor traffic without manipulating it.
- Hardware protocol analyzers are used to monitor and identify malicious network traffic generated by hacking software installed in the system.
- They capture a data packet, decode it, and analyze its content according to certain rules.
- Hardware protocol analyzers allow attackers to see individual data bytes of each packet passing through the cable.
- These hardware devices are not readily available to most ethical hackers due to their enormous cost in many cases.
- Lawful Interception (LI) is defined as legally sanctioned access to communications network data such as telephone calls or email messages. LI must always be in pursuance of a lawful authority for the purpose of analysis or evidence. Therefore, LI is a security process in which a network operator or service provider gives law enforcement officials permission to access private communications of individuals or organizations.
- Almost all countries have drafted and enacted legislation to regulate lawful interception procedures; standardization groups are creating LI technology specifications. Usually, LI activities are taken for the purpose of infrastructure protection and cyber security. However, operators of private network infrastructures can maintain LI capabilities within their own networks as an inherent right, unless otherwise prohibited.
- LI was formerly known as wiretapping and has existed since the inception of electronic communications.