With Ubuntu's uncomplicated firewall, using terms like allow or deny translate into an easy to follow method for blocking unwanted port access.
The biggest benefit in having a firewall on the Linux desktop comes down to controlling the data flowing back and forth. If there is random data flowing in and out of an insecure port, then it's reassuring to have the ability to easily block it. While it might not be an immediate threat, in the future, that same port could be used maliciously. So port control is a nice feature indeed.
As we've learned during the well documented Heartbleed incident, nothing that executes code is ever going to be 100% secure. Claiming otherwise is misleading and inherently false. To the casual end user, the only difference with regard to security is that installable malware isn't an issue. Phishing, hacking exploits, and issues of a compromised network are still things to remain vigilant about.
To further summarize and offer actionable tips to keep your Linux box secure, remember the following:
And there you have it. As a general rule, the Linux desktop does indeed offer a secure computing environment, but even with its security in place it pays to use the tips provided above as a failsafe measure.