Constantly listening on a port - Security issue?

[godsstigma]

Hello everyone,

I am a hobbyist coder and am writing an app for basic communications over the web. It consists of a program that listens on a port for a info and a program to send a very particular string.

Now the program that listens only reacts when it receives this certain string but it is constantly listening on a certain TCP port.

I know virtually nothing about networking.

How big of a security threat is this?

As it is just for a learning experience I can provide the source if requested.

Thanks – John-Paul

[systemErr]

It can be huge. But that's why people use firewalls, to close those ports. Listening ports just wait to receive a signal to "go." Windows has open ports all the time though... just go to command prompt and type netstat -a to see.

[johnwill]

Truthfully, if your program doesn't have things like buffer overflow vulnerabilities, it's not that big a threat. After all, that's how any server application runs, right?

[godsstigma]

Originally Posted by systemErr

It can be huge. But that's why people use firewalls, to close those ports. Listening ports just wait to receive a signal to "go." Windows has open ports all the time though... just go to command prompt and type netstat -a to see.

Ok, so I also use RealVNC that is constantly listening on a port for a connection. Isn' t this just as vulnerable?

Truthfully, if your program doesn't have things like buffer overflow vulnerabilities, it's not that big a threat. After all, that's how any server application runs, right?

I am using a function library for the TCP connections that was written in C++.
I know that C++ is notorious for buffer overflow. I do not know C++. what do you think?

[johnwill]

It's what is called an "attack surface". The more ports you open, the larger the attack surface, and the easier it is for an attacker to find a bug that allows him in the door. The trick is to minimize the attack surface as much as possible. Obviously, if you want the server functionality, you can't eliminate it totally.