2 - Raspberry PI Community Projects

features imply a increased risk of a vulnerability hiding in the code; picking the most advanced
program for a task may actually be counter-productive, and a better approach is usually to pick
the simplest program that meets the requirements.
VOCABULARY
Zero-day exploit
A zero-day exploit aack is hard to prevent; the term covers a vulnerability
that is not yet known to the authors of the program.
14.5.4. Managing a Machine as a Whole
Most Linux distributions install by default a number of Unix services and many tools. In many
cases, these services and tools are not required for the actual purposes for which the administrator
set up the machine. As a general guideline in security matters, unneeded software is best
uninstalled. Indeed, there's no point in securing an FTP server, if a vulnerability in a different,
unused service can be used to get administrator privileges on the whole machine.
By the same reasoning, firewalls will often be configured to only allow access to services that
are meant to be publicly accessible.
Current computers are powerful enough to allow hosting several services on the same physical
machine. From an economic viewpoint, such a possibility is interesting: only one computer to
administrate, lower energy consumption, and so on. From the security point of view, however,
such a choice can be a problem. One compromised service can bring access to the whole machine,
which in turn compromises the other services hosted on the same computer. This risk
can be mitigated by isolating the services. This can be attained either with virtualization (each
service being hosted in a dedicated virtual machine), or with SELinux (each service daemon
having an adequately designed set of permissions).
14.5.5. Users Are Players
Discussing security immediately brings to mind protection against attacks by anonymous crackers
hiding in the Internet jungle; but an often-forgotten fact is that risks also come from inside:
an employee about to leave the company could download sensitive files on the important
projects and sell them to competitors, a negligent salesman could leave their desk without locking
their session during a meeting with a new prospect, a clumsy user could delete the wrong
directory by mistake, and so on.
The response to these risks can involve technical solutions: no more than the required permissions
should be granted to users, and regular backups are a must. But in many cases, the
appropriate protection is going to involve training users to avoid the risks.
QUICK LOOK
autolog
The autolog package provides a program that automatically disconnects inactive
users aer a configurable delay. It also allows killing user processes that
persist aer a session ends, thereby preventing users from running daemons.
Chapter 14 — Security
403