Depends on the network. Cisco routers support Access Control Lists (ACLs) for perimeter/border security; Cisco PIX supports Security Policies for firewall (or 2nd level of defense) security ? both support Secure Shell (SSH) encryption and anti-spoofing and anti-Denial of Service (DoS) attacks, to name a few options. Servers support TCP/IP filtering and auditing. Application layer firewalls further compliment network firewalls and Intrusion Detection Systems (IDS). Desktop firewall also compliment network firewalls. Read through my series for security tips on improving network security.
Dig deeper on Network Security Monitoring and Analysis
Related Q&A from Retired Expert - Luis Medina
Why is it considered to be problematic to send digital data over the PSTN and how are these problems
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.