ufw
ファイアウォールです。
$ ufw --help Usage: ufw COMMAND Commands: enable enables the firewall disable disables the firewall default ARG set default policy to ALLOW or DENY logging ARG set logging to ON or OFF allow|deny RULE allow or deny RULE delete allow|deny RULE delete the allow/deny RULE status show firewall status version display version information Application profile commands: app list list application profiles app info PROFILE show information on PROFILE app update PROFILE update PROFILE app default ARG set profile policy to ALLOW, DENY or SKIP