ISPs are generally expected to disclose any port blocking. A quick Google search shows this is Frontier’s list: http://www.frontierhelp.com/faq.cfm?qstid=277 On 3/25/15, 10:31 PM, "Aaron C. de Bruyn" <aaron@heyaaron.com<mailto:aaron@heyaaron.com>> wrote: I've had a handful of clients contact me over the last week with trouble using SCP (usually WinSCP) to manage their website content on my servers. Either they get timeout messages from WinSCP or a message saying they should switch to SFTP. After getting a few helpful users on the phone to run some quick tests, we found port 22 was blocked. When my customers contacted Frontier, they were told that port 22 was blocked because it is used to transfer illegal files. I called them, and got the same ridiculous excuse. Just a friendly heads-up to anyone from Frontier who might be listening, I have a few additional ports you may wish to block: 80 - Allows users to use Google to search for illegal files 443 - Allows users to use Google to search for illegal files in a secure manner 69 - Allows users to trivially transfer illegal files 3389 - Allows users to connect to unlicensed Windows machines 179 - Allows users to exchange routes to illegal file shares 53 - Allows people to look up illegal names -A