Normally, your VoIP service provider should take care of security in your communication. This means that they should have a proper firewall running, they should have reliable authentication technologies in place, and they should provide encryption for voice transmission.
Most service providers are making big efforts to put adequate security measures into place. Most of them are not up to the level of reassuring users fully, though. This is why it is important that you consider security as one of the factors when choosing a service provider. Speak to them about that if you want detailed information.
As an example, many providers have a firewall built-in on the routers or ATA’s they provide. But this is not as reliable as a firewall which runs on a computer, as the latter can be tweaked for better performance.
A firewall needs to be configured, and very often, you might have to change your firewall settings to allow the traffic from and to your VoIP service. If you have problems with your firewall, seek help from its manual, FAQs (frequently asked questions), or email its support team.
Even if the service provider should take care of the VoIP service security, you can consolidate that security on your part. You may, for instance, install and run a firewall on your server or computer. Read more on firewalls here.
