Port Scanner with PRTG

Ports are endpoints that make it easier for all the different processes and services on your network to talk to each other. When ports are working as they should, data flows freely and your network runs smoothly. But when ports are misconfigured or have other issues, they can slow your network down and make you more vulnerable to trojans and other security risks.

Ports are part of a network address (IP address). They ensure TCP connections and data packets are assigned correctly and allow for the processing of services on the Internet. This may involve the transfer of files (ports 20 and 21) with the file transfer protocol (FTP), the sending of an email (port 25) via SMTP and IMAP, the SSH (Secure Shell) port 25, or the assignment of names to an IP address (Port 53) in a domain name system (DNS). Ports use a transport protocol to transmit information. Each port is assigned a non-random number. These port numbers range from 0 to 65535, with 1 to 1023 used for Internet protocols.

A transport protocol – aka a “network protocol” – specifies how data is to be exchanged between the components in a network. In other words, it defines the way in which data is transmitted. The two most common protocols are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP). PRTG can be used as a port scanner for both TCP and UDP scans.

A port scanner is a tool that checks the status of ports. It uses queries to determine whether a port is open, closed, or hidden.

• Open port: The computer accepts the query, responds, and asks what to do next.
• Closed port: The computer responds to the query and indicates that the port is in use and therefore unavailable.
• Hidden port: The computer provides no response to the query. The port may be hidden, filtered, locked, or blocked.

Some port scanners also scan open ports for additional information (such as the operating system in use), but this is not their primary purpose.

Port scanners work in a variety of ways. The simplest (and most common) way involves the uninterrupted transfer of data to a specific host. The port scanner notifies the system as soon as a data packet reaches an open port. Data packet types can also vary: TCP, UPD, ICMP, FIN, and ACK are just a few examples.

Port scanners can scan both vertically and horizontally. With vertical scans, a single network address is scanned on multiple ports. Horizontal scans, on the other hand, test several network addresses on a specific port (e.g., port 80).

Port monitoring is like surveillance, while port scanning is an inspection. A port monitoring tool helps you track overall performance and identify long-term trends. A port scanner, on the other hand, is how you spot potentially imminent threats, such as ports that are open when they should be closed.

PRTG port scanner regularly sends network requests to your chosen port and tracks how long it takes for the port to receive it. This enables it to identify whether the port is open or closed, and what devices, applications, or other services it's being used for.

PRTG is designed to scan ports using TCP. But you can also scan ports using UDP by creating a custom script.

In PRTG, “sensors” are the basic monitoring elements. One sensor usually monitors one measured value in your network, for example the traffic of a switch port, the CPU load of a server, or the free space on a disk drive. On average, you need about 5-10 sensors per device or one sensor per switch port.