This application probes the host or server to identify open ports such as port 21 for FTP. These can be used by black hat hackers and bad actors to exploit vulnerabilities by finding out running network services. Moreover, they are also used by security analysts to confirm network security policies. These 8 best free online port scanners can help you prevent a network breach by showing you the open ports you have on a server or network.
Port scanning is an important part of the step of securing your online infrastructure or servers. It allows you to identify weaknesses in your server and networks that may allow a hacker to gain access and steal confidential customer data that you may hold such as email addresses.
Types of Online Port Scans
Port scan has been designed to carefully send prepared packets to each destination port number. Following are a few basic techniques that it is capable of.
Xmas and FIN Scans
This is a great example of a suit of scans that is used to collect information without being logged by the target system. In this, an unsolicited FIN flag is sent to the port. The system’s response to this will reveal the port state or insight regarding the firewall.
A closed port will get an unsolicited FIN packet, but an open port will ignore it. This sends flag sets, creating nonsensical interaction. The system’s response can be interpreted to understand the port and firewall of the system.
FTP Bounce Scan
This allows the sender’s location to be disguised by bouncing the packet via the FTP server. Moreover, in this, the sender is not detected.
Vanilla
This is basic among all scans, connecting you with all 65,536 ports one at a time. This sends the SYN flag and on receiving the SYN-ACK response, it sends back ACK flag. This exchange will compromise the TCP handshake. Full connect scans are quite accurate in nature and can be detected easily as full connections are always logged by firewalls.
Sweep Scan
This is designed to ping the very same port across systems to identify which system on the network is active. Now, this will not give out any information regarding the state of the port. It tells the sender which systems on the network are active, thus it is used as a preliminary scan. This scan method works similarly to a mass search against multiple hosts and audits them like Wifite does on wireless networks.
SYN Scan
This is also known as a half-open scan which sends SYN and waits for the response from the target. The scanner will never respond once the response is received. Since the TCP connection was not completed, the system shall not log interaction, but the sender gets to know whether the port is open or not.
8 Best Online Port Scanner For 2023 (Free Tools)
Port scanners come in all shapes and sizes, below is a list of the best port scanning tools that can be used online/offline and are totally free. We have also included a table for comparison between online and offline port scanner utilities:
| Online Port Scanner | Traditional Port Scanner for PC |
|---|---|
| Can be accessed from anywhere in the cloud | Can only be accessed from one PC or Laptop |
| Sometimes can cost money to use and require a subscription | Does not require a subscription |
| Your data lives on a server somewhere in the cloud | Your data and port scan results live locally on your drive |
| Your data can be accessed by third-party companies in-case they have a breach | Your data is safe as it lives within your PC, laptop or VM |
| As they are online, you are dependent on their uptime promise | You can access your port scanning tool at any time as you wish and are not bound to anyone elses uptime or maintenance windows |
TCP Port Scanner – Best Free Online Port Scanner
It scans TCP Ports only. It uses the SYN method and is capable of scanning up to ten thousand ports per second. It has compatibility with Windows only.
Zenmap (NMAP GUI) – Free Port Scanner Tool
This is not a very new port scanner but an official NMAP front-end interface. For those unfamiliar with command line terminals, the creators of Nmap launched this GUI which will allow you to scan remote hosts that too in a friendly way.
It helps to save scan results in the database, save all port scan files for port discover options that are frequently used, search results in the database and compare current scan results with previous scans.
Nmap (Network Mapper) – Top Online Port ScannerÂ
This is abbreviated as Network Mapper, a favorite tool of administrators around the globe. Hackers and penetration testers also use it to test the security of servers and networks for any open ports that may be listening and can be closed if not needed.
Nmap can also do OS fingerprinting allowing you to find out which operating system is running on a server or endpoint. It can also go the extra step to showing specific software running such as an Apache Web Server or SQL Database.
NetScanTools – Best Advanced Port ScannerÂ
This is premium toolbox that carries with it around 50 tools for DNS, Discovery, Traceroute, Ping, SNMP, Whois, ARP and many others.
It is compatible with some port scans including TCP/UDP ICMP, TCP full connect, TCP SYN half-open, UDP ICMP and others, including a combination of PSH, RST, SYN, ACK, and PSH.
RELATED READ: Download Kismet WiFi Hacker App for Android in APK File.
Unicornscan – UDP Port Scanner free for PC
This is quite a popular tool due to its asynchronous TCP and UDP scanning capabilities and non-common network discovery patterns that provide alternate ways to get details regarding remote OS and services.
This helps in asynchronous stateless TCP scanning and enables different modules from the command line, asynchronous UDP scanning, remote OS detection and IP port scanner and service detection.
Angry IP Scanner – Reliable IP Port Scanner for PC
This is another free option on the list which has compatibility with MacOS X and Windows. It features to scan IP addresses and ports.
Moreover, it also fetches NetBIOS information, detect web servers, scan favorite IP addresses and a lot more.
The scan results are saved into TXT, XML, CSV or as IP-Port lists.
Netcat – Accurate Port ScannerÂ
This is an old tool that was developed back in 1995 whose last version is from 2004. It has many forks and variants that work well on modern OS such as ncat from the Nmap suite or this alternate Netcat version from MikeFrysinger.
This is also used for huge range of objectives such as opening remote connections, run remote commands, port scanning and tunneling and proxying.
MiTeCÂ Network Scanner – TCP Port Scanner Online
These multipurpose advanced scanner tools have been designed to scan IP, port AD, ICMP, SNMP and NetBIOS. This downloads major Windows operating systems 32 or 64-bit.
In this you can import a list of devices and export results data into CVS format. It has been designed to scan TCP and UDP both and get a built-in Whois checker feature.
Other security-related tools you may like:
- Top 7 Malware Analysis Tools for Python Code.
- 5 Best Code Vulnerability Scanner Tools.
- How To Find Website Admin Credentials of any CMS.
Conclusion
This was the end of our article on the 8 best port scanners online that you can use for free. Please let us know which port scanner is your top pick as ours has to be Nmap followed by Netcat and TCP Port Scanner that cover all TCP and UDP scanning. Do let us know how you are using these, is it on a VM in the cloud or locally hosted or do you rely solely on offline solutions? Have a nice day!
Frequently Asked Questions
Which is the best free online port scanner?
There are various port scanners available but based on speed, agility and tcp port scan speed, Nmap is one of the best port scanners available online that is also free to use.
Is it legal to use Port Scanning Tools?
Port scanning is only legal if you are scanning networks and servers that you have access to do so on. It is illegal to scan or hack into networks and servers that you do not have or otherwise have written permission to do so on.
Are Online Port Scanners reliable and accurate?
Different port scanning tools will give you different result outputs based on their quality and protocols they support such as TCP or UDP. Hence you should always compare the results and use the tool that works best for you.
