5. Running Exim as a daemon

On a Debian system, Exim will run from inetd (8). This is dangerous because an attacker can stop Exim working by opening many (100 will be enough) connections to it, preventing it to handle any more connection.

You can avoid this attack by running Exim as a daemon. Edit the file /etc/inetd.conf as root.
#:MAIL: Mail, news and uucp services.
smtp           stream  tcp     nowait  mail    /usr/sbin/exim exim -bs
Add # to the "smtp" line.
#:MAIL: Mail, news and uucp services.
#smtp           stream  tcp     nowait  mail    /usr/sbin/exim exim -bs
Then Exim will run as a daemon when you boot the system next time. To run Exim as a daemon without reboot, do as root:
# /etc/init.d/exim start