A

P P E N D I X

D

Glossary

his appendix defines some of the most commonly used terms in this

T

book.

Alert A message generated when any intruder activity is detected. Alerts may be sent

in many different forms, e.g., pop up window, logging to screen, e mail and so on.

DMZ

Demilitarized zone.

HIDS

Host Intrusion Detection System. A system that detects intruder activity for a

host.

IDS Intrusion Detection System. A system that detects any intruder activity. Snort is

an example of an IDS.

IDS Signature A pattern that we want to look for in a data packet. Based upon a par 

ticular signature we can define appropriate action to take.

NIDS Network Intrusion Detection System. This is an intrusion detection system that

works for a network. Usually a device (computer or a dedicated device) is placed at

an appropriate location in the network to detect any intruder activity.

Rule Header The first part of each Snort rule. It contains information about action,

protocol, source and destination addresses, port numbers and direction.

Snort Configuration File The snort.conf file, which is the main configura 

tion file for Snort. It is read at the time when Snort starts.

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