TCP Port Scanner

Find Open TCP Ports with Online Port Scanner 

Find Open TCP Ports with Online Port Scanner 

What Is An Online Port Scanner?

In order to secure the network perimeter of a company, finding out which network services are exposed to the Internet is key.  

With an online port scanner, you can easily discover open communication channels on computer systems through accurate port discovery and service detection. Prevent attackers from identifying vulnerabilities and easy access to your network.

Compared to using a port scanner on your local machine, the main difference when using an online version is that, if you do the same scan from your internal network, your firewalls and network restrictions may produce different results.

Plus, our TCP Port Scanner is:

Why Use Scantrics TCP Port Scanner Online?

Contents of the Report

Here is what you can expect in Scantrics’ TCP Port Scanner (Full Scan) report:
TCP Scanner

Use Cases for TCP Port Scanner

The TCP Port Scanner provides network administrators with an overview of the network attack surface including all open TCP ports and services from an attacker’s perspective.

Since the attacker will also use port scanning to discover a potential way in, network administrators can use the results of the TCP Port Scanner to develop better security countermeasures.

The TCP Port Scanner is a tool that allows organization to run checking/fingerprinting on the network infrastructure. It is capable of detecting the port status on the target device along with the service and service version.

Running an in-depth scan with TCP Port Scanner provides organizations with useful information to determine the proper services that should be utilized on the infrastructure.

Running TCP Port Scanner against the target device allows network administrators to check the current configuration of the company’s firewall. As the generated report will display the TCP port, service, and service version information, the network administrator can identify any TCP port that should and should not be open or listening to any connection.

Therefore, network administrators can identify which source IP should be allowed to connect to a particular port. The tool also helps find any service version that needs to be updated to prevent attackers from exploiting outdated software.

Technical Details

TCP stands for Transmission Control Protocol. TCP Protocol is located on Layer 4 on the OSI layer which is one of the main protocols of the internet. TCP protocol is a standard protocol used to exchange data between devices in the network.

TCP takes messages from an application/server and divides them into packets, which can then be forwarded by the devices in the network to the destination. TCP is connection-oriented protocol which means that the connection will be established and well-maintained until the data exchange between applications/servers is completed.

The portion of data exchanged through TCP protocol is formatted as “TCP Segment” which contains a header and data, where a header will hold information about the source port number, source IP, destination port number, and destination IP.

Devices that connect to each other using TCP protocol will need to perform three-way handshake, which is SYN-SYNACK-ACK.

  1. First, the source device will contact the destination device and ask if the destination device is available through a certain port by sending SYN flag.
  2. Second, if the device at the destination has the port open as requested, then it will send back the response by giving SYNACK flag.
  3. Third, the source device will send ACK flag as a response to the destination device.

In TCP protocol, any packet lost can be detected as it is connection-oriented protocol, thus the connection will make sure that the data packets are completely exchanged between the two servers/applications.

TCP protocol is always used for a connection that requires the data to be delivered completely to ensure the reliability of the information. TCP protocol is best suited to be used for applications that require high reliability instead of timing, such as HTTP/HTTPS application, Secure Shell (SSH), File Transfer Protocol (FTP), Email (SMTP, IMAP/POP), etc.

However, any TCP connection can be intercepted and analysed by an attacker as well. Attackers are capable of inspecting the traffic and seeing what data passes through the traffic. For example, any data exchanged through port 80 (HTTP) can be intercepted and read as plain text by the attacker as there is no encryption mechanism. Therefore, the attacker is able to run the same port scan and see the information regarding the port, service, and service versions on the target server.

Therefore, it is really important for a network administrator to have the right tool in order to check and verify the information returned by the scanner and then to come out with the proper security countermeasures before the attacker performs the attack.

  • 21 – FTP (File Transfer Protocol)
  • 22 – SSH (Secure Shell)
  • 23 – Telnet
  • 25 – SMTP (Mail)
  • 80 – HTTP (Web)
  • 110 – POP3 (Mail)
  • 143 – IMAP (Mail)
  • 443 – HTTPS (Secure Web)
  • 445 – SMB (Microsoft File Sharing)
  • 3389 – RDP (Remote Desktop Protocol)

The TCP Port Scanner has two types of scans, which are Quick Scan and Full Scan.

What services are available under Quick Scan?

  • Check for the most common Top 100 TCP ports.
  • Service detection.
  • Service version detection.

What services are available under Full Scan?

Full Scan performs all the services of Quick Scan but with custom parameters for port scans that can be easily configured from the web interface

  • Specify custom TCP ports to scan (1-65535)
  • Enable/disable service detection
  • Enable/disable operating system detection
  • Enable/disable host discovery
  • Do Traceroute

Additionally, users of TCP Port Scanner can schedule periodic port scans to continuously monitor the attack surface of your network perimeter.

How it works?

How it works

TCP Port Scanner is based on the most powerful port scanner, Nmap. Nmap is known as the de-facto tool for finding open ports and services, allowing users to run a set of scans against the target host.

As such, TCP Port scanner functions the same way as Nmap does. Users only need to define the target IP/Hostname and the tool will do DNS resolution before sending the request to the target.

Firstly, it will perform host discovery in order to check if the host is live before probing the ports on the target. Then, the tool will run open port detection script in order to detect the listening port on the target and it will also perform service detection for the particular port. For example, when TCP Port Scanner finds there is port 80/443 open on the target, it will check what services are running, such as Apache, Nginx along with other versions.

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