In this modern era, organizations greatly rely on computer networks to share

Signature-based IDS
o
It needs a database of known attacks with their signatures. 
o
Signature is defined by types and order of packets characterizing a 
particular attack. 
o
Limitation of this type of IDS is that only known attacks can be detected. 
This IDS can also throw up a false alarm. False alarm can occur when 
a normal packet stream matches the signature of an attack. 
o
Well-known public open-
source IDS example is “Snort” IDS. 
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Anomaly-based IDS
o
This type of IDS creates a traffic pattern of normal network operation. 
o
During IDS mode, it looks at traffic patterns that are statistically unusual. 
For example, ICMP unusual load, exponential growth in port scans, etc. 
o
Detection of any unusual traffic pattern generates the alarm. 
o
The major challenge faced in this type of IDS deployment is the difficulty 
in distinguishing between normal traffic and unusual traffic. 

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Summary 
In this chapter, we discussed the various mechanisms employed for network access 
control. The approach to network security through access control is technically 
different than implementing security controls at different network layers discussed in 
the earlier chapters of this tutorial. However, though the approaches of 
implementation are different, they are complementary to each other. 
Network access control comprises of two main components: user authentication and 
network boundary protection. RADIUS is a popular mechanism for providing central 
authentication in the network. 
Firewall provides network boundary protection by separating an internal network from 
the public Internet. Firewall can function at different layers of network protocol. 
IDS/IPS allows to monitor the anomalies in the network traffic to detect the attack and 
take preventive action against the same. 
Network Security – Critical Necessity 
Information and efficient communication are two of the most important strategic 
issues for the success of every business. With the advent of electronic means of 
communication and storage, more and more businesses have shifted to using data 
networks to communicate, store information, and to obtain resources. There are 
different types and levels of network infrastructures that are used for running the 
business. 
It can be stated that in the modern world nothing had a larger impact on businesses 
than the networked computers. But networking brings with it security threats which, if 
mitigated, allow the benefits of networking to outweigh the risks. 
Role of Network in Business 
Nowadays, computer networks are viewed as a resource by almost all businesses. 
This resource enables them to gather, analyze, organize, and disseminate 
information that is essential to their profitability. Most businesses have installed 
networks to remain competitive. 
The most obvious role of computer networking is that organizations can store virtually 
any kind of information at a central location and retrieve it at the desired place through 
the network. 
Benefits of Networks 
Computer networking enables people to share information and ideas easily, so they 
can work more efficiently and productively. Networks improve activities such as 
purchasing, selling, and customer service. Networking makes traditional business 
processes more efficient, more manageable, and less expensive. 
The major benefits a business draws from computer networks are − 
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