Information
The INFO parameter specifies that record login and logout activity will be logged. While this is the default setting for OpenSSH we believe it is better to explicity set the value in the configuration file.
Rationale:
SSH provides several logging levels with varying amounts of verbosity.
LogLevel
Gives the verbosity level that is used when logging
messages from sshd(8). The possible values are:
QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1,
DEBUG2, and DEBUG3. The default is INFO. DEBUG and
DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
higher levels of debugging output. Logging with a
DEBUG level violates the privacy of users and is not
recommended.
DEBUG (and VERBOSE) is specifically not recommended other than strictly for debugging SSH communications. INFO level is the default level and records login/logout activity of SSH users. Login information includes the fingerprint of their SSH keys, when used.
In situations, such as Incident Response, an SSH fingerprint may be important to determine when a particular user was active on a system. The logout record can eliminate those users who disconnected, which helps narrow the field.
Note: the default action of OpenSSH is to propagate this key for every ssh login.
Solution
Edit the /etc/ssh/sshd_config:
vi /etc/ssh/sshd_config
Set:
LogLevel INFO
Re-cycle the sshd daemon to pick up the configuration changes:
stopsrc -s sshd
sleep 2
startsrc -s sshd
Default Value:
#LogLevel INFO