Most third party software will require that one or more ports be available since they have one or more data feeds / protocols required to communicate either their or their partners servers.
The reality of the world right now is that you really cant have all communications as secure as we would like: there are many third party applications that transmit/receive data in a nonsecure manner and for now we just have to live with these mechanisms. Unfortunately it is costly to open firewall ports - which introduces the requirement for monitoring and filtering the open ports in most situations, thus adding costs/overhead.
Some data/trading providers do provide the option of a Virtual Private Network (VPN) option for their customers: however it appears to me that very few offer this option currently.