Para permitir o login de apenas alguns usuários, você pode usar a palavra-chave AllowUsers em / etc / ssh / sshd_config. Para restringir um número de conexões ssh Você pode usar a palavra-chave MaxSessions .
Por exemplo:
AllowUsers jack joe
MaxSessions 5
Do manual:
AllowUsers This keyword can be followed by a list of user name patterns, separated by spaces. If specified, login is allowed only for user names that match one of the patterns. Only user names are valid; a numerical user ID is not recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from partic- ular hosts. The allow/deny directives are processed in the following order: DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.