Chapter 03. Scanning Networks

Overview of Network Scanning

  • Network scanning refers to a set of procedures for identifying hosts, ports, and services in a network.
  • Network scanning is one of the components of intelligence gathering an attacker uses to create a profile of the target organization.
  • Objectives of Network Scanning:
    • To discover live hosts, IP address, and open ports of live hosts
    • To discover operating systems and system architecture
    • To discover services running on hosts
    • To discover vulnerabilities in live hosts

TCP Communication Flags

  • URG (Urgent): Data contained in the packet should be processed immediately
  • FIN (Finish): There will be no more transmissions
  • RST (Reset): Resets a connection
  • PSH (Push): Send all buffered data immediately
  • ACK (Acknowledgement): Acknowledges the receipt of a packet
  • SYN (Synchronize): Initiates a connection between hosts

TCP/IP Communication

Creating Custom Packet Using TCP Flags

  • Colasoft Packet Builder enables creating custom network packet to audit networks for various attacks.
  • Attackers can also use it to create fragmented packets to bypass firewalls and IDS systems in a network.

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