# Chapter 8. kppp and Security Issues

This section is mainly for superusers (root), people with high security demands or simply technically interested people. It is not necessary to read this if you only use Linux at home for yourself (though you might learn something new when you read this)

# 8.1. Restricting access to kppp

A system administrator might want to restrict access to who is allowed to use kppp. There are two ways to accomplish this:

## 8.1.1. With group permissions

Create a new group (you might want to name it "dialout" or similar), put every user that should be allowed to use kppp into that group and type:

     chown root.dialout /usr/local/kde/bin/kppp
     chmod 4750 /usr/local/kde/bin/kppp

This assumes that KDE was installed in `/usr/local/kde` and your new group is named "dialout".

## 8.1.2. kpppīs way

Before doing anything, kppp checks if there is a file named `/etc/kppp.allow`. If such a file exists, ONLY users named in this file are allowed to dial out. This file must be readable by every user (of course NOT writable). Only login names are recognised, thus you cannot use UIDīs in this file. Hereīs a short example:

     # /etc/kppp.allow
     # comment lines like this are ignored,
     # as well as empty lines
     fred
     karl

     # I put myself in here :-)
     mweilguni

In the example above only the users fred, karl and mweilguni can use kppp to dial out, as well as every user with a UID of 0. So you donīt need to put root in this file.