Terms you'll need to understand:
Types of threats
Threat mitigation
Console access
VTY access
Authentication methods
Types of services
Access control lists (ACLs)
Threat mitigation using ACLs
Techniques you'll need to master:
Securing console access
Securing VTY access
Securing passwords
Securing Simple Network Management Protocol (SNMP)
Disabling router services and interfaces
Following rules for creating ACLs
Configuring ACLs for threat mitigation