Adversaries may use Valid Accounts to log into remote machines using Secure Shell (SSH). The adversary may then perform actions as the logged-on user.
SSH is a protocol that allows authorized users to open remote shells on other computers. Many Linux and macOS versions come with SSH installed by default, although typically disabled until the user enables it. The SSH server can be configured to use standard password authentication or public-private keypairs in lieu of or in addition to a password. In this authentication scenario, the user’s public key must be in a special file on the computer running the server that lists which keypairs are allowed to login as that user.
|M1042||Disable or Remove Feature or Program||
Disable the SSH daemon on systems that do not require it. For macOS ensure Remote Login is disabled under Sharing Preferences.
Require multi-factor authentication for SSH connections wherever possible, such as password protected SSH keys.
|M1018||User Account Management||
Limit which user accounts are allowed to login via SSH.
|ID||Data Source||Data Component||Detects|
|DS0028||Logon Session||Logon Session Creation||
Monitor for user accounts logged into systems that may use Valid Accounts to log into remote machines using Secure Shell (SSH). For example, on Linux systems SSH logon activity can be found in the logs located in
|DS0029||Network Traffic||Network Connection Creation||
Monitor for newly constructed network connections (typically port 22) that may use Valid Accounts to log into remote machines using Secure Shell (SSH). Use of SSH may be legitimate depending on the environment and how it’s used. Other factors, such as access patterns and activity that occurs after a remote login, may indicate suspicious or malicious behavior with SSH.
Monitor for newly executed processes that may use Valid Accounts to log into remote machines using Secure Shell (SSH). For example, on macOS systems