How to identify open ports
The following are the six port states that are present in Nmap:
open: This means that the port is functioning and has a service running or accessing it. The service can thus accept any connections made as per the protocol and service in use on this port.closed: A closed port is not being accessed by any service, there is no service running on it. Thus, no connections made externally will be successful on these ports.filtered: This status is associated with ports from which no response was received due to the packet filtering mechanism present within the network. This might be caused by an intermediate network protection device.unfiltered: This status is associated with the ports that Nmap was not able to determine whether they were open or closed. Mostly ACK scan labels ports to be in unfiltered state; moreover, scans such as SYN and FIN can help resolve such issues.Open|filtered: Nmap classifies ports with this type when no response is received from them. The...
