An intrusion-detection system (IDS) is a software-based tool used to detect for crackers or other security breaches such as incoming shellcodes, viruses or trojan horses in a computer system or network.
Two main types of intrustion detection system exists:
... the population is spread out with 21.7% under the age of 18, 5.1% from 18 to 24, 32.6% from 25 to 44, 31.2% from 45 to 64, and 9.4% who are 65 years of age or older. ...