Nessus has detected that the remote SSH server is configured to use the Arcfour stream cipher or no cipher at all. RFC 4253 advises against using Arcfour due to an issue with weak keys.

The remote host answers to an ICMP timestamp request. This allows an attacker to know the date that is set on the targeted machine, which may assist an unauthenticated, remote attacker in defeating time-based authentication protocols. Timestamps returned from machines running Windows Vista / 7 / 2008 / 2008 R2 are deliberately incorrect, but usually within 1000 seconds of the actual system time.

The SSH server is configured to support Cipher Block Chaining (CBC) encryption. This may allow an attacker to recover the plaintext message from the ciphertext. Note that this plugin only checks for the options of the SSH server and does not check for vulnerable software versions.

The remote SSH server is configured to allow either MD5 or 96-bit MAC algorithms, both of which are considered weak. Note that this plugin only checks for the options of the SSH server, and it does not check for vulnerable software versions.

The remote SSH server is configured to allow key exchange algorithms which are considered weak. This is based on the IETF draft document Key Exchange (KEX) Method Updates and Recommendations for Secure Shell (SSH) RFC9142. Section 4 lists guidance on key exchange algorithms that SHOULD NOT and MUST NOT be enabled. This includes: diffie-hellman-group-exchange-sha1 diffie-hellman-group1-sha1 gss-gex-sha1-* gss-group1-sha1-* gss-group14-sha1-* rsa1024-sha1 Note that this plugin only checks for the options of the SSH server, and it does not check for vulnerable software versions.