A.P. Lawrence

This article is from a FAQ concerning SCO operating systems. While some of the information may be applicable to any OS, or any Unix or Linux OS, it may be specific to SCO Xenix, Open Desktop or Openserver.

There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.

TCP/IP and NFS FAQ

How do I secure services on a SCO system?

First, consider that production machines should never be firewalls. Two important functions like that should be on separate machines. However, you shouldn't just depend on a firewall either; each internal machine should be at least reasonably secured by shutting off unnecessary services etc.

Many services are run by the inetd daemon. You turn them off by editing /etc/inetd.conf, commenting them out, and either rebooting or sending inetd a signal 1 (which tells it to re-read inetd.cong).

cite>Some people edit /etc/services. I think that's wrong, because inetd.conf is what really controls inetd. Services is the just translation of names to numbers, and I think it's potentially confusing to do it the other way, because anyone looking at it would think that the service could run.

For example, find the fingerd in /etc/inetd.conf and put a # sign at the beginning of the line. Then signal inetd

 kill -1 `cat /etc/inetd.pid`

Some things (like http) are started in the scripts at /etc/rc2.d. You stop them by running (for example)

 /etc/rc0.d/K78atlas
 /etc/rc0.d/S90fasttrack

Those scripts stop the SCO Netscape servers.

To keep them from starting again, you need to edit

/etc/rc2.d/S90atlas and /etc/rc2.d/S90fasttrack

and put "exit 0" at the top of each script. Or skip the K78atlas etc. and just reboot after adding the "exit 0" to these scripts. (you can also start and stop individual servers through the Netscape Admin server rather than just stopping everything)

A very few things start in /etc/tcp, for example snmp and ntp. You'll find lines like :

 if [ -x /etc/ntp.conf ] ; then
 /etc/ntpd -g
 fi

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To stop that one from starting, you'd remove or rename /etc/ntp.conf. What happens there is the the "-x" tests to see if /etc/ntp.conf exists; if it does, then "/etc/ntpd -g" is run. If it does not exist, nothing happens. You'd need to reboot for these to take effect, or you could run

 /etc/tcp stop
 /etc/tcp start

after making your changes, or track down what you have disabled with "ps"

 ps -e | grep routed

and kill each process manually.

Finally, consider running tcpwrappers and/or ipfilters. See http://aplawrence.com/Security/general.html and http://aplawrence.com/Security/ipfilter.html