This makes it impossible for an attacker to abuse the Webif for probing the root password.
Attempts to login as root are intentionally no answered with any meaningful error message but just "401 - Authentication required", just as if you entered wrong credentials.
In order to use this feature, you first have to telnet/ssh to your box and enter (for example):
adduser admin -h /dev/null -H -s /bin/false -G rootplus a password for this new user (twice).
This will create a new user
- named "admin"
- with /dev/null as his home dir (Does not exist)
- with /bin/false as shell (can not login to shell ...)
- being a member of the group "root" (Doesn't mean anything without the ability to get to a shell)
and the password as chosen by you ... (Preferably NOT the same as that for user "root").
Group "users" or any other existing group should work as well.
After creating one (or multiple) users != "root", you can use their credentials for login and disable root logins.