Back in section 7.1 on page [*], we discussed file permissions in
Linux. This is a fundamental way to keep your system secure. If you
are running a multi-user system or a server, it is important to make
sure that permissions are correct. A good rule of thumb is to set
files to have the minimum permissions necessary for use.
If you are running a network server, there are some other things to
be aware of as well. First, you ought to uninstall or turn off any
network services you’re not using. A good place to start is the file
/etc/inetd.conf; you can probably disable some of these. For most
/network
services, it’s also possible to control who has access to them; the
/etc/hosts.allow and /etc/hosts.deny files (documented in
man 5 hosts_access) can control who has access to which services.
You also ought to keep up-to-date with patches or updates to Debian;
these can be found on your nearest Debian FTP mirror.
Some other commonsense rules apply:
◼ Never tell anyone your password.
◼ Never send your password in cleartext across the Internet by
using something like telnet or FTP. Instead, use encrypted
protocols or avoid logging in remotely.
◼ Avoid using root as much as possible.
◼ Don’t install untrusted software, and don’t install it as root.
◼ Avoid making things world-writable whenever possible. /tmp is
one exception to this rule.
While this is probably not of as much use to somebody not running a
server, it is still pays to know a bit about security. Debian’s
security mechanism is what protects your system from many viruses.