Only allow root ssh access to the server
 

When creating 10 samba users I also created Linux users. I do not want these Samba users to be able to use putty, winscp etc to access the server.

Do you know how I can restrict ssh access to specific users?

DenyUsers? or, better AllowUsers?
man sshd_config
Anyway, why would you need root access to ssh? isn't it better to allow one user to access ssh and then use sudo/su when need root access?

Alternatively (or additionally), you could give the samba users nologin shells.

# chsh -s /sbin/nologin user_here

I don't use samba, but I don't see why a valid shell would be required. (However, if I am mistaken, then my advice is wrong. ;))

This is the way to go if your concerns are the samba users only.
If you dont want any other user then root, use Allow/DenyUsers

Also, when you create a samba user, it does need a system user.
BUT (and this is important to know) you do not need to set a password on the system user account.
This automatically does deny ssh access as empty password logins are denied by ssh.

Bear in mind setting the shell to nologin does not prevent non-shell ssh access, like portforwarding. And there's a nice little DoS using that. To block ALL types of ssh access, you need to use Allow/Deny users

And you should not allow root ssh logins. If you allow root logins, an attacker need only guess the root password. You should allow a user to login to ssh, and then su to root. And make the root password different to the user's password. That way, an attacker has to guess a username, a user password, and a root password.

Yes, forgot to mention the non shell ssh access :) (-N option). Good you mentioned that!

Thanks guys, good advice. I've changed my approach, now only one user account has ssh access and has to su to root.