A sniffer is a program or a device that eavesdrops on the network traffic by grabbing information traveling over a network. Sniffers basically are “Data Interception” technology.
In packet-switched networks, the data to be transmitted is broken down into several packets. These packets are reassembled once all the data packets reach their intended destination.
When a packet sniffer is installed in the network, the sniffer intercepts the network traffic and captures the raw data packets. Subsequently, the captured data packet is analyzed by the packet sniffing software and presented to the network manager/technician in a user-friendly format. By user-friendly, we mean the Network Administrator should be able to make sense of it.
There are 2 basic types of Ethernet environment and how sniffers work in both these cases is slightly different.
- Shared Ethernet: In a shared Ethernet environment all hosts are connected to the same bus compete with one another for bandwidth. In such an environment packets meant for one machine are received by all the other machines.
- Switched Ethernet: An ethernet environment in which the hosts are connected to switch instead of a hub is called a switched Ethernet. The switch maintains a table keeping track of each computer’s MAC address and the physical port on the switch to which that MAC address is connected and delivers packets destined for a particular machine correspondingly. The switch is an intelligent device that sends packets to the destined computer only and does not broadcast it to all the machines on the network, as in the previous case. This results in better utilization of the available bandwidth and improved security.
Though a switch is more secure than hub, the following methods can still be used to sniff on a switch:
1. ARP Spoofing
Using arpspoof to poison the ARP cache of a machine is accomplished by giving the command:
root@mint:~# arpspoof -t 192.168.0.131 192.168.0.136
dc:53:60:2b:e7:47 94:65:9c:20:9c:7a 0806 42: arp reply 192.168.0.136 is-at dc:53:60:2b:e7:47
dc:53:60:2b:e7:47 94:65:9c:20:9c:7a 0806 42: arp reply 192.168.0.136 is-at dc:53:60:2b:e7:47
2. MAC Flooding:
root@mint:~# macof
4e:f3:64:3d:17:17 11:92:23:7d:6a:51 0.0.0.0.389 > 0.0.0.0.60438: S 1713527361:1713527361(0) win 512
66:3e:8:6b:fd:38 d6:1c:b3:75:8a:45 0.0.0.0.50476 > 0.0.0.0.52504: S 94222295:94222295(0) win 512
Warning: This method might lead to degeneration of the network service and should not be run for a long interval of time.
Detecting Sniffers:
A sniffer is usually passive, it just collects data. Hence it becomes extremely difficult to detect sniffers, especially when running on a shared Ethernet. But it is slightly easier when the sniffer is functioning on a Switched Ethernet network segment. When installed on a computer, a sniffer does generate some small amount of traffic.
- Ping Method.
- ARP Method.
- On Local Host.
- Latency Method.
- ARP Watch.
- Using IDS.
Preventing Sniffing:
The best way to secure our self against sniffing is to use encryption. While this won’t prevent a sniffer from functioning it will ensure that what a sniffer reads are pure junk
If we are on a switched network, the chance is that arp spoofing will be used for sniffing purpose. The machine that the malicious user will most probably try to arp-spoof is the gateway. To prevent this from happening, we can add the MAC address of the gateway permanently to our ARP cache. This can be done by placing the MAC address of your gateway and other important machines in the /etc/ethers file.
Switch to SSH. SSH is fast becoming the de facto standard method of connecting to a Unix/Linux machine. For more information on SSH, check out http://www.ssh.fi. We might want to check out the open-source implementation OpenSSH at http://www.openssh.org/
Instead of using HTTPS if the site supports it. In Case we are really bothered about the privacy of our mail.
Programs to detect sniffers:
- Anti sniff.
- Neped.
- ARP Watch.
- Snort.
FAQs
The ping method is useful in detecting a system that runs in promiscuous mode, which in turns helps to detect sniffers installed on the network. Just send a ping request to the suspected machine with its IP address and incorrect MAC address.
Are packet sniffers easy to detect? ›
Challenges with Packet Sniffing Response
It's difficult to spot the hacker because they might look like an authorized user or even a system administrator.
Which tool is associated with network sniffing? ›
Wireshark is a free open source tool that analyzes network traffic in real-time for Windows, Mac, Unix, and Linux systems. It captures data packets passing through a network interface (such as Ethernet, LAN, or SDRs) and translates that data into valuable information for IT professionals and cybersecurity teams.
Which command can be used to check if a sniffer is being run in a promiscuous mode? ›
Many operating systems provide a mechanism to determine whether a network interface is running in promiscuous mode. This is usually represented in a type of status flag that is associated with each network interface and maintained in the kernel. This can be obtained by using the ifconfig command on UNIX-based systems.
What is a sniffer in networking? ›
A network sniffer, also known as a packet analyzer, is either software or hardware that can intercept data packets as they travel across a network. Admins use network sniffers to monitor network traffic at the packet level, helping ensure network health and security.
Is network sniffing illegal? ›
Packet sniffing is illegal when access to data packets is unauthorized. Hackers use packet sniffing to monitor and steal data, which is also an illegal use of packet sniffing.
What is the best defense against packet sniffing? ›
Data encryption. To combat packet sniffing, one should consider implementing data protection and encryption solutions. Data encryption is an excellent choice for individuals and professionals against sniffing. Tunnel your connectivity using Virtual Private Network (VPN) to protect yourself from packet sniffers.
Can Wireshark be detected? ›
Wireshark is passive collector of information. It produces no signature on a network. Therefore, unless you are shoulder surfing the person running wireshark or have direct access to their device, you will not know.
Can you prevent packet sniffing? ›
The best way to prevent packet sniffing is to use encryption and authentication methods for your network traffic, as mentioned above. These methods can ensure that only authorized parties can access or modify your data, and that your data is protected from eavesdropping or manipulation.
What is a sniffer IP address on a network? ›
What is IP Sniffing. An IP sniffer software intercept, extract, and analyze useful information such as source and destination IP addresses, port and protocols, and other relevant data from the header and the payload of a network packet.
Sniffing is the term generally used for traffic monitoring within a network, while port scanning is used to find out information about a remote network. Both sniffing and port scanning have the same objective—to find system vulnerabilities—but they take different approaches.
What is sniffer trace? ›
A Sniffer details packet transfer, and thus a Sniffer trace analysis can help pinpoint switch and McAfee® Network Security Platform performance or connectivity issues when the issues persist after you have exhausted the other suggestions in this document.
Which tool is an example of a packet sniffer? ›
Packet Sniffer – Packet sniffing is done by using tools called packet sniffer. It can be either filtered or unfiltered. Filtered is used when only specific data packets have to be captured and Unfiltered is used when all the packets have to be captured. WireShark, SmartSniff are examples of packet-sniffing tools.
Which mode should a sniffer operate on? ›
Promiscuous mode is used to monitor(sniff) network traffic.
Which tool is used for sniffing? ›
Wireshark
One of the best and widely used tools for sniffing and spoofing is Wireshark. Wireshark is a network traffic analysis tool with a plethora of capabilities. Wireshark's extensive library of protocol dissectors is one of its most distinguishing features.
What is an example of a sniffer tool? ›
1. Wireshark. Wireshark is a popular open-source, cross-platform network protocol analyzer, or a packet sniffer in other words, that captures packets from a network connection.
What is passive sniffing techniques? ›
Passive Sniffing
It works with Hub devices. On a hub device, the traffic is sent to all the ports. In a network that uses hubs to connect systems, all hosts on the network can see the traffic. Therefore, an attacker can easily capture traffic going through.
What can a Wi-Fi sniffer see? ›
A network sniffer “sniffs” or monitors network traffic for information (e.g., where it's coming from, which device, the protocol used, etc.). Network administrators can use this information to help optimize their environment.
Can network sniffers decipher encrypted traffic? ›
Encryption does not prevent packet sniffers from seeing source and destination information, but it does encrypt the data packet's payload so that all the sniffer sees is encrypted content.
Is sniffing public Wi-Fi illegal? ›
Legality: Packet sniffing can be legal under certain circ*mstances, such as when it's done with the explicit consent of network owners or when it's done for the purpose of network security analysis. However, in many cases, packet sniffing without permission is illegal and can result in criminal charges.
