Securing Debian

2006-07-27 Linux

One thing I do when I have installed Debian is to tighten it down slightly. There are some great scripts to do this, such as bastille and also the securing debian howto but here is my top 10 lockdowns:

Secure users home directories

chmod -R 700 /home<br /> vi /etc/adduser.conf
Disable all services not used and make sure that sshd is running on protocol2.
Disable ftp (use ftpd-ssl or scp instead) and telnet (you should be using ssh)
Disable root from accessing sshd, so only a normal user can log on then su.
Configure logcheck to send logs to an outside email address.

apt-get install logcheck

vi /etc/logcheck/logcheck.conf

If you need to change the frequency, edit the cron file here:

vi /etc/cron.d/logcheck
Get regular updates from your apt sources
Restrict system reboots/shutdown on the console:

vi /etc/inittab
```
ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
```
vi /etc/shutdown.allow<br /> Add your users in that are allowed to shutdown the system when logged in

Edit pam.d security files to match your security policy:

cd /etc/security
Consider using tripwire to monitor any changes in binaries on your system.
Take a backup of the system. Always a good policy.