network isolation

Succeeds: firewall & IDS

Concept

Firewall

• gateway to the internet
• isolates an organization’s internal net from the larger internet
• allows some packets to pass, but blocks others
• why?
  • prevent denial of service attacks
  • prevent illegal access/modification of internal data
  • allow only authorized access
• types:
  • stateless packet filter
  • stateful packet filter
  • application gateway
• limitations:
  • IP spoofing - src IP might not be true
  • single point of access - bottleneck, tradeoff between degree of communication and level of security

Stateless packet filter

• filter packet by packet
• at the router -
• filter based on:
  • src/dest IP
  • TCP/UDP src/dest port
  • ICMP message type
  • TCP SYN/ACK

Access control list

• sequential set of ruls
• applied to all incoming packets in order
• determines if a packet should be allowed or denied