The swatch package continuously scans for events in syslog that you, the systems administrator, define and then when it spots something of interest it alerts you. See their man pages for more details. Other security measures firewalling A firewall in computers is a device that protects a private network from the wider internet. The Firewall computer can reach the protected network and the internet. This protected network cannot reach the internet, and the internet cannot reach the protected network.
All data flowing to and from the internet and the private network is filtered by the firewall.
Inside the private network less care needs to be taken with turning off services and the like. It is a way of concentrating effort on making one machine secure and protecting many others in the process. The methods for correctly setting up fireballs are quite complex. First you have to configure your machine for two Ethernet cards. Then you have to use the ipchains software to setup filters which connect the two ethernet cards data links.