Opening a port on my router, is it safe?

It isn't quite that simple but ultimately yes you'll need to open the incoming port for your IP address in your router configuration otherwise the request coming to the router will be blocked. Since you're using IIS and you're talking about an API I assume you're using the default 443 port for SSL. Opening that up should be fine.

What you need to consider though is that opening up that port means anyone can send a request to your IIS server for any sites on your server. If you end up hosting multiple sites then that could be problematic. What is generally recommended is that your site bindings only respond to a very specific DNS name (e.g. myserver.org) and this will at least ensure that you're only responding to specific DNS requests.

Another issue to consider though is that your IP address isn't static on the INet. Your ISP has only a limited range of IPs it can use. So when you connect to your ISP they give you an IP address. There is no guarantee you'll get the same IP each time. Even more complicated is the fact that your IP can actually change while you're connected. The general workaround for this is to request a static IP from your ISP but that costs more money. If you're going that route then you'll probably want to register a DNS name as well so callers can use your DNS name and not a static IP address that could change over time.

I wonder about your entire setup though. Are external callers actually calling you directly or are you calling external apps to get data. If you're setting up a system where callers can call you at any time then hosting this locally is probably not a good idea. You should consider hosting all this either on a hosting site or in the cloud. This will eliminate a lot of the security concerns, need for port forwarding, static IPs and even potentially DNS records as hosting providers handle this for you. The cloud is also an option if you don't want to go the hosting provider route.

Ultimately if you host a public facing server on your own network then you do put your network at risk if the server is compromised. You also have to manage the "always on" needs of the application, network usage (since an app could call you 100s of times a second), backups, etc. If you pay for bandwidth by usage then having external calls to you could eat that up rather quickly. As a test this might be doable but I wouldn't do this as a permanent solution.

It will only be as safe as the code is safe. You want to be sure to use a standalone locked down computer to host the app. you may want to add DOS attack prevention.

note: as you asked this question, you likely do not have the network security background to make this completely safe, or detected an attack. You should really look at a hosting service. If only as a proxy to your on-prem service.

Hello John R,

Thank you for your question. Opening a port on your router—commonly referred to as port forwarding—can be necessary for certain applications (e.g., hosting a web server, remote desktop, gaming), but it does come with security implications that should be carefully considered.

Is It Safe?

Opening a port is not inherently unsafe, but it does expose a service on your internal network to the internet, which increases your attack surface. Whether it's safe depends on:

• What service is exposed
• How well that service is secured
• Whether proper firewall and access controls are in place

Best Practices for Safe Port Forwarding:

1. Only Open What You Need

Avoid opening ports “just in case.”

Close any ports that are no longer in use.

2. Use Strong Authentication

Ensure the service behind the port requires strong passwords or multi-factor authentication.

Avoid exposing services that don’t support secure authentication (e.g., older FTP or Telnet servers).

3. Restrict Access by IP

If possible, configure your router or firewall to allow access only from specific IP addresses.

4. Use Non-Default Ports

While not a security solution by itself, using a non-standard port can reduce exposure to automated scans.

5. Monitor Logs and Traffic

Use router logs or a network monitoring tool to watch for unusual access attempts.

Additional Resources:

Microsoft Docs – Port Forwarding

OWASP – Secure Configuration Guidelines

Shodan.io – Use this to check if your public IP is exposing any open ports or services.

Summary:

Opening a port is safe only if the service behind it is secure, access is controlled, and you understand the risks. If you're unsure, using a VPN or cloud-based service is often a safer alternative.

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