Filtering Rules

Service-Dependent Filtering

• Permit incoming Telnet sessions only to a specific list of internal hosts
• Permit incoming FTP sessions only to specific internal hosts
• Permit all outbound Telnet sessions
• Permit all outbound FTP sessions
• Deny all incoming traffic from specific external networks

Service-Independent Filtering

• Deny SNMP options like giving routing table
• Inspect for specific IP options
  • Source Routing Attacks
  • Tiny Fragment Attacks.
  • Checking for a special fragment offset