Basic techniques of scanning.

  1. Ping Sweep
    Ping sweep is scanning a range of ip address one by one to check whether the target ip is alive or not . in this technique a range of ip address is defined in the same ping command just like : ping 123.43.23.45/24, the whole range of ip address is scanned until or unless live target is found .
    This technique is mainly used when there is no specified target and hence targets the whole network to get live target.
  2. Transmission control protocol (TCP)
    Tcp contains flag , sniffing into tcp flags can provide information to a greater extent . There are following flags present in tcp:
    A. SYN: Synchronize , initiates the connection between two systems.
    B. FIN: Finish , Indicates that transmission is finished
    C. ACK: Acknowledgement , Establish the connection
    D. RST: Reset , used for resetting the connection established
    E. URG: Urgent gives packet a priority to process immediately
    F: PSH: Push , instruct the target to respond with buffer data immediately.
  3. 3-Way Handshake Mechanism

    3-way handshake is used for successful transmission of information or successful connection establishment .
    3-way Handshake process

  • The system A will initiate a connection request to the server via a packer with only SYN FLAG.
  • Server will reply back with packet having both SYN & ACK Flag set
  • Now the client responds back to the server with a single ACK packet
  • If the above steps are completed without any problem or complication , then  a TCP connection will be established b/w the client and server.
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