Affected NAS devices had reached end-of-life, but there is a patch, so make sure to protect your endpoints straight away.
https://www.techradar.com/pro/security/mirai-esque-botnet-is-hitting-zyxel-nas-devices
https://www.techradar.com/pro/security/mirai-esque-botnet-is-hitting-zyxel-nas-devices