} I'm curious what is considered striping down a box? I can understand
} the obvious stuff like /usr/games, and maybe a few binaries in /bin
} and /usr/bin, along with most setuid binaries. Possibly even remove
} the compiler, though compiling on an alternate box is real easy. So
} what can be done? top strip it down?
Well personally I do this from the other end...
The firewall type boxes I build are based on Red Hat Linux. This uses a
fairly fine grained package system based on RPM packages, but you can do
something similar with other package based systems.
I work my way through all the packages that are part of the normal
distribution and select which ones I actually want and throw everything
else out. I set the install defaults to not install any documentation
(mainly to reduce the number of excess files around). I rebuild a number
of packages (relatively small) to have different defaults, configurations
or authentication (although with the advent of PAM this last is becoming
less necessary - all I need is a decent OTP module). I add some packages
on for specific functions, and I build a new kernel package with the
kernel configured as I want (no modules, very small number of necessary
drivers, anti SYN measures etc...).
Nothing is installed on the box that isn't from a package other than a
*very* small number of config files - in general you can do
rpm -qif /some/file
on any file other than the stuff in /tmp and /var/spool and find that it
belongs to a specific package.
I also install some monitoring stuff including tripwire (yes RPM can do
package verification, Tripwire does system verification).
As to compilers etc... I do not install compilers. However parts of my
system require perl and I do install that. If someone is on the box you
are pretty much shot anyhow... As much as possible does not run as root
and is chrooted.
In summary I suggest you design what the box is for, not hack a few things
off a general purpose box, and you focus everything you install on the box
to the purpose of the box.
[ Nigel .
net - Systems Software Engineer ]
[ Tel : +44 113 251 6012 Fax : +44 113 224 0003 ]
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