All about Secure Shell
Content of the article
Secure Shell, abbreviated as SSH — this standard allows directives to be sent securely to a remote computer over an insecure network. It uses encryption and authentication techniques to ensure secure connections between devices. In addition, SSH supports tunneling, which allows information to be transferred through channels that are not normally intended for this purpose.
SSH: functions, tasks, implementation paths
SSH performs two main functions:
- Establishes an encrypted remote connection. The protocol establishes a communication channel between the user's device and a remote machine, often a server. This channel uses encryption to ensure that the transmitted data is secure from eavesdropping. To an outside observer, the information in this channel looks like random useless combinations.
- Organizes tunneling. Tunneling — it is a way of sending data over a network using a protocol or route that it would not normally use. SSH uses port forwarding techniques to direct packets from one machine to another. This makes it possible to bypass network restrictions and deliver information to different places where they would not reach via normal routes.
How SSH works
Secure Shell operates based on the TCP/IP protocol suite, which is quite common on the Internet. TCP ensures that data is delivered in the correct order, and IP indicates where this data should be sent. Together they form the basis of network communication, and SSH uses this infrastructure to create a secure communication channel.
In addition, SSH uses public key encryption techniques to authenticate and encrypt information. Each side of the connection has its own dual set of keys: public and private. The public key is available to everyone, but only the owner of the private key can decrypt messages encrypted with the public key. This approach ensures the security and authentication of communications.
Using SSH allows administrators to remotely manage servers, infrastructure and employee computers without fear for the privacy and security of data. SSH is also widely used for securely exchanging files, connecting to remote services, and bypassing firewall restrictions.
Despite these advantages, SSH can have weak points that can be attacked, especially if its settings are not sufficiently secure or if the keys to access servers fall into the hands of attackers. Therefore, you need to monitor the security of your SSH configuration and regularly update access IDs to minimize threats.
Scope of application of SSH
SSH is pre-installed on Linux and Mac OS. For Windows, you may need to install SSH client software. Mac and Linux users are free to open the system's built-in Terminal and issue SSH directives without installing additional applications.
The most common use cases for SSH include:
- Remote control of servers, infrastructure and employee computers.
- Secure file sharing. SSH provides greater security than unencrypted protocols such as FTP.
- Connect to cloud services without the need for unlocking ports on a local computer on the Internet.
- Remote connection to services on a private network.
- Bypassing firewall restrictions.
What port is needed for SSH and what cyber threats exist for this protocol?
SSH uses the standard port 22. Sometimes firewalls block access to some open network access points on servers, but leave port 22 open. Because of this feature, SSH can be useful for logging into servers outside the firewall: packets directed to port 22 are not are blocked, they can be redirected to another network point.
In theory, every protocol can be hacked, but SSH's encryption and free tunneling attract the attention of cybercriminals. There have been cases where SSH has been used to extract sensitive information, create backdoor routes in a relatively secure network, and even gain free entry into server configurations.
Some types of attacks are aimed at stealing SSH keys for the purpose of unauthorized entry into a network of private computers and servers. Storing and generating SSH keys is a major security issue for large companies that manage thousands or millions of keys, but keeping track of and updating them regularly is nearly impossible. If an attacker obtains the key, they theoretically have permanent access to the network for an extended period of time.
What is the difference between SSH and other tunneling protocols?
One of the main differences between SSH and other tunneling protocols is what layer of the OSI model they operate at. Some protocols, such as GRE, IP-in-IP and IPsec operate at the network layer and are unaware of ports, working only between IP addresses. SSH operates at the application layer (OSI Layer 7), which allows it to encrypt only specific applications rather than all traffic.
Another difference is the use of the TCP SSH protocol. TCP guarantees data delivery in order and without loss, unlike UDP, used for example in IPsec. Although protocols using UDP may be faster, they do not provide the same reliability as TCP.
Finally, SSH only encrypts individual applications, while IPsec encrypts all network traffic, regardless of its origin. This makes SSH less suitable for setting up a VPN.
Private VPN server: a modern digital product
SSH does not provide the full functionality that is typically expected from modern VPN servers, such as scalability, session management, and support for various protocols. Therefore, when considering issues of ensuring data security on a large number of devices or for corporate networks, it is more advisable to pay attention to private VPN servers. This type of server typically offers a broader range of features, including the ability to scale to serve large numbers of users, efficient session management, and support for multiple protocols, providing a more reliable and flexible network security solution.
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