strongly recommended idea is that you keep upto date reading and
looking at papers and DoS articles on the programs that you use,
it is suggested that you update your programs as frequently as possible.
(this is where RPMS and up2date by Red Hat come in very handy)
Yet another problem for securing your machine are services that
are running on your machine but not being used at all, these can
provide easy attack points if they are well know to have little
security holes, to better secure your machine you should not run
anything that is not being used. Some
of these services include, Apache, FTP, Sendmail, Samba, Telnet
(especially if you only use SSH) and any other ones you may have
running. Each of these can be shutdown without any problems, and
you should use linuxconf
to set them not to start automatically when your machine boots.
Another thing that
is recommended is to get rid of the default FTP program that comes
with Linux and install ProFTPd, this is a nicer and more secure
FTP daemon (server) and is quite easy to setup. For downloading
and instructions, visit the homepage http://www.proftpd.net/.
For installation help please visit the programs section of the
this site, located here.
If you are
ever hacked or getting problems (DoS attack or similar) then it
is a good idea to block the IP of the person who they came from,
this can be done by adding the IP to the file /etc/hosts.deny.
As usual keeping your software up-to-date is the best way of insuring
the security of you machine is high. If your running Red Hat 7.0
then you can use the up2date program to update certain parts of
the system, other distributions may have a similar mechanism for
updates but otherwise it is up to you to upgrade with new RPMS,
new source and a better Kernel when they are released.
idea is to keep your eyes out and read articles on programs that
you are installing on your machine (as mentioned previously),
some have small security holes (most which can be fixed with a
simple update or patch install) or some may have major problems.
If you find that a particular program you are running is susceptible
to a DoS attack or a tricky little backdoor via a coding bug then
its imperative that you find the appropriate fix or temporarily
shutdown that program or service.
a Linux machine is only as secure as you make it, if your worried
about being hacked or have been hacked then you should really
think about upgrading the security on your machine. This is a
simple started guide and you can go on to more complex methods
from here. Hope that this helps some of you out. Any comments
then please feel free to e-mail me mayhem (at) linuxathome.net,
for specific help with firewalls I recommend e-mailing the authors
of the described scripts.