For arbitrary port ranges and continous monitoring with alerts, we hope you'll consider creating an account once we are ready. Most functions will still be free.
Need to do something more in-depth?
While we are building our login system so you can scan things with more precision and with alerts, we aren't ready yet. So in the meantime if you want to scan host systems more thoroughly, there are software applications you could try in the meantime. A popular free option for Apple Macintosh users is the built-in Network Utility. If you are a Windows user, you can take a look at Advanced Port Scanner.
Please use caution when installing random software from the Internet on your Windows computer. Unfortunately there's no good built-in way to scan with Windows like there is for Mac users and it is a popular technique for people to package up 'free' software with spyware. While we don't really care for Norton's product line in general, they have an excellent write up that they provide about how to avoid getting spyware from free download packages.
What do these results mean?
If the results of a scan indicate that you have open ports, it means that your computer is responding to network requests at those ports. For example, if you have installed Apache on your computer and then scanned it, you would probably expect it to respond on port 80 with a YES. If our scanner reports back with a YES result, your system is reachable by the public via the Internet with no firewall or other obstacle. If you are installing common server software and trying to test it with the scanner and you get a NO, there could be a firewall issue, an issue with port forwarding or possibly an issue with the software using an unusual port that we don't check.
It is normal for all computers to have open ports that they respond to as this is the basis for TCP/IP communication, so do not be alarmed in general if you see an open port on your system. However, our scanner is scanning from the public internet, which means if we can see it, so can anyone connected to the internet. If you do not want your computer system responding to everyone on the internet, it may be worthwhile to purchase a proper firewall and take some preventative measures to hide your system from the public.
Does having open ports indicate security problems?
The common ports that we scan do not typically indicate a security issue. However, it depends a bit on what you are scanning. If you are scanning your home PC and find a ton of open ports, this is actually a bit unusual. Normally your home router blocks all incoming requests by design so you should see mostly NO results when performing a scan or ping check. On the flip side of the open ports issue, if you have ports open on purpose that you use often and the software reports it as closed, the software responding may have crashed or been misconfigured. If you have an account on web portscanner, you can monitor for changes in port status if you want to be alerted to a service popping up or closing down.
What are the specific uses for these ports?
A basic breakdown of what is in the free scan:
Port 21 - FTP - This is the classic file transfer protocol.
Port 23 - Telnet - This is a very old and simple terminal server. It is insecure and in modern times used to configure routers or other devices via command line interface.
Port 25 - SMTP - This one is the Simple Mail Transfer Protocol. SMTP is very insecure and if you are not deliberately running a mail server this could indicate a spyware infection on a home PC or an open relay on a server that was meant for another task.
Port 53 - DNS - This indicates a Domain Name Server which converts web addresses into IP addresses.
Port 80 - HTTP - Port 80 is the common web server port used not only for serving web pages but for controlling NAS devices and interacting with routers and switches. This open port is not normally a surprise even on your home computers. Try putting the name or IP address into your web browser if you aren't sure what service or software may have opened this port up.
Port 110, 995 - POP3 - The post office protocol is the service that allows you to check for mail. This would be unusual when seen on other than a system that hosts email of some kind.
Port 443 - HTTPS - This is typically indicative of a secure/encrypted web server, although it could be used for any encrypted data. Again, entering the name or ip into your browser may bring up the service that opened this port for you to view.
Port 465, 587 - Secure SMTP - These ports are associated with sending email in a secure fashion. The 587 is the more modern of the two. This would be unusual on systems that aren't expected to be relaying email.
Port 993 - IMAP - This indicates availability of an IMAP style mail server for checking email. Typically only seen on systems that host email.
Port 1433 - MS SQL Server - If this shows on the open internet, it could be a major security risk. If you are actively using SQL Server your data is likely exposed to attack, if not, it is possible an application opened up this port and is just wasting resources on your system.