Scanning Networks

Scanning Networks

1. Why do we scan networks?

   • Discovers a network's live hosts, IP Addresses, open ports
     • Discovers the Operating System and System Architecture
       • Discovers running services and listening on the target Systems - gives the indication of Vulnerability
         • Identifies applications or versions of a particular service

2. TCP Communication Flags

   • Synchronize - Notifies transmission of a new sequence number, represents establishment of a connection (3 way handshake)
     • Acknowledgement - Confirms receipt of transmission & identifies next expected sequence number
       • Push - Sends all Buffered Data Immediately
         • Urgent - Data contained in the packet should be processed immediately
           • Finish - There will be no more transmission
             • Reset - Resets a connection
   • SYN, ACK, FIN & RST - governs the establishment, maintenance, termination
     • PSH and URG - provide instructions
       • Total of 6 BITS
         • Colasoft Packet Builder
           • Enables creating custom network packets to audit networks for various attacks
             • Attackers can also use it to create fragmentated packets to bypass firewalls and IDS systems in a network