What is Scanning Networks ?

1. Network scanning is a procedure for identifying active hosts on a network, either for the purpose of attacking them or for networksecurity assessment.
2. Network scanning is a procedure for identifying active hosts on a network, either for the purpose of attacking them or for network security assessment. Scanning procedures, such as ping sweeps and port scans, return information about which IP address map to live hosts that are active on the Internet and what services they offer. Another scanning method, inverse mapping, returns information about what IP addresses do not map to live hosts; this enables an attacker to make assumptions about viable addresses
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   OverView of Network Scanning

1. Network scanning refers to a set of procedures for identifying osts,ports,and services in a network
2. Network scanning is one of the components of intelligence gathering an atttacker uses to create a profile of the target organization.

   Checking For Live Systems ICMP Scanning

     Ping scan involves sending ICMP ECHO Requests to a host. If the host is live,it will              return    an ICMP ECHO Reply

   This Scan is useful for Locating active devices or determining if ICMP is passing through      firewall

 

    Ping Sweep

   ping sweep is used to determine the live hosts from a range of Ip address by sending          ICMP ECHO requests to multiple hosts

   Attacker calculate subnet masks using Subnet mask calculators to identify the numbers      of host present in the subnet

   Attackers use ping sweep to create an inventory of live systems in the subnet

  Three Way Handshake

  TCP uses a three way handshake to establish a connection between server and client

 Scanning Tool : Nmap

 Attacker uses Nmap to extract information such as live hosts on the network services 

 Tcp Connect / Full open Scan

• Tcp connect scan detects when a port is open by completing the three way handshake 
• Tcp connect scan establishes a full connection and by sending a RST packet

 Stealth Scan

•  Attackers use stealth scanning techniques to bypass firewall rules, logging mechanism  and hide themselves as usual network traffic

 FIN SCAN

•  Attacks send a TCP frame to remote host with only Fin flags set
•  FIN scan only with os tcp/ip developed according to rfc 793

NULL SCAN

 

•  Attacker send a Tcp frame to a remote host with no flags
•  It will not work against any current version of microsoft windows