Network security is an over-arching term that describes that the policies and procedures implemented by a network administrator to avoid and keep track of unauthorized access, exploitation, modification, or denial of the network and network resources.
This means that a well-implemented network security blocks virus, malware, hackers, etc. from accessing or altering secure information.
The first layer of network security is enforced through a username/password mechanism, which only allows access to authenticated users with customized privileges. When a user is authenticated and granted specific system access, the configured firewall enforces network policies, that is, accessible user services.
However, firewalls do not always detect and stop viruses or harmful malware, which may lead to data loss. An anti-virus software or an intrusion prevention system (IPS) is implemented to prevent the virus and/or harmful malware from entering the network.
Network security is sometimes confused with information security, which has a different scope and relates to data integrity of all forms, print or electronic.