Secure Shell (SSH) - E 115: Introduction to Computing Environments (2024)

• SSH permits secure login connections and file transfer over the Internet or other untrusted networks.
• Cryptographic algorithms are used to authenticate both ends of the connection, to automatically encrypt¹ all transmitted data, and to protect the integrity of data²
• SSH has the ability to “tunnel” information and applications through a host. You send your information to a host, which forwards it to its actual destination.

SSH protects against:

• IP spoofing – a remote host sends out packets which pretend to come from another trusted host.
• IP source routing – a host can pretend that an IP packet comes from another trusted host.
• DNS spoofing – an attacker forges name server records
• Interception of clear text passwords and other data by intermediate hosts
• Manipulation of data by people in control of intermediate hosts
• Attacks based on listening to X authentication data and spoofed connection to the X11 server
• Essentially protects against any network attack

SSH does not protect against:

• A malicious user gaining root access to host (remote) machine
• A malicious user gaining root access to the recipient machine

1. Encryption is a process of translating plaintext information into a ciphertext. To properly decrypt information, a computer must know which “key” to use as reference. This way, only authorized parties can understand the information. ↩︎
2. Ylonen, T. (1996, July). SSH–secure login connections over the Internet. InProceedings of the 6th USENIX Security Symposium(Vol. 37, pp. 40-52).
   Chicago ↩︎