It is usually not relevant to the story how a technology (or magic) works.
Most people don't know how smartphones work, or computers, or cars. We just use them and have some grasp of their capabilities and limitations. That's what matters most to the story: what you can and can't do with them.
Readers are a diverse group with different levels of knowledge
Computer-savvy readers/viewers like us know what a firewall is (to some extent), and an "offensive firewall" may raise some questions for us. But most readers have no clue and don't care. It's not actually important to the story, but it can distract readers like us and break immersion. So to that extent it's important to think about.
I think there are two options here: 1) avoid such terms. Ideally, you want to keep all your readers on board all of the time. But that may be difficult, your readers are a diverse group and you may not be able to please all of them all of the time. And you need something to hack the enemy's computer. And you need to call it something. So maybe it's best to pick a name that sounds plausible to the casual reader and go for option: 2) Rely on your readers' suspension of disbelief. Most readers are perfectly willing to let something implausible or nonsensical slide if it makes for a good story. Faster-than-light travel? Sure. Time-travel? Why not. Magic? Of course.
If you need to explain, still try to show, not tell
The guideline of "show, don't tell" is about speaking to the readers' imagination. Instead of giving them dry facts, you want them to be emerged in the story and experience it vividly. You can still use that approach for explaining things like technology, magic or physics as well.
Let's take gravity as example:
I could say "gravity is a force between two masses, the strength of which is proportional to each mass and inversely proportional to the distance squared". This is, to a good approximation, true. But it's a bit dry, and hard to get an intuition for what it really means.
Another explanation is "Consider space as a stretched rubber sheet. If you put a large object like a bowling ball on it, it curves 'space', creating a sort of well near the ball. Then, if you put a marble near it, it will naturally roll down the gravity well toward the large mass. But if you give the marble enough speed, it will move in circles around the bowling ball. That's how planetary orbits work."
The second explanation speaks a lot more to the imagination. (And it gives the right intuition for light bending under the influence of gravity.)