To disable this, you have 2 options:

1) Recommended: Disable this in the web user interface (depends a little on the QTS version your QNAP is running)

Goto "Control Panel" - "General Settings" (in the "System" section) - "Console Management".
There you uncheck the option "Enable Console Management" and click "Apply".

2) If you QNAP does not have the option in "Control Panel".

SSH into your QNAP and edit the file

/etc/profile

find the line (most likely the last line) that starts with:

[] && /sbin/qts-console-mgmt -f

Comment out this line (add a "#" in front of it).

Alternatively, you can use this one liner that you can run in the shell directly (I recommend doing this manually though):

sed -r -i.bak 's/^(.*admin.*qts-console-mgmt.*)$/#\1/' /etc/profile