[Samba] how to access public shares without password even when security = user

[Athanasios Silis]

Hello everyone,
I have always thought that with security = user , a login window will pop-up
and you must insert credentials to access the shares of a samba server.

Yet here I am sitting in front of a QNAP system file server, running Samba
3.5.2. When I type in the address of the samba server, I am presented with
the top level shares (public or not). No login window pops up.. Then if I
try to access some of these shares (that are not public), a login in window
will pop up..
I checked the QNAP's smb.conf thoroughly and found the following

security = USER
map to guest = Bad User

I used the 'map to user' option in another samba server i have (slackware64
v13.37) Samba v.3.5.10. I also allowed guest users
I almost mimiced the behaviour. I.e. I access the samba server, a login
window pops up, i can type in some random characters and will access the
shares without the need for a proper username password.

But I want to omit having a login window pop up in the top level of the
shares. how should I go about doing that? (of course that will map me to
some guest user and give me access to public folders. the private folders
should still throw a login window at me)

Thank you for your help

Nass