GFI LANguard detects that the specific port is open. It is possible that a legitimate application is using the port, but it is also possible that the machine is infected with the virus indicated. The information shown in the banner may help you determine whether it is a legitimate application or not. Most of the backdoor viruses will provide a banner that says what they are.
It is recommended to scan the target machine with a virus scanner to ensure that no virus or other malicious software is running on the scanned machine.
If you have local access to the machines, you may find out what is running on what port by running the following command:
netstat a b
The -b parameter will list which application is using that port.