Is it really possible to put a virus in a machine you don't know? [duplicate]

I believe it would be possible because the Harvesters already showed that their technology was compatibles with ours.

Before the first wave of the attack David discovered that the Harvesters were using our satellites to communicate with the mother ship by embedding their own signal. Dave already worked out that the signal was recycling itself into nothing

David: I've got a lock on the signalpattern. We can filter it out.
Marty: Huh? Oh, good, hood.
David: Strange thing is, if my calculations are right it'll be gone in approximately seven hours anyway. The signal reduces itself every time it recycles. Eventually it will disappear. Are you listening?

The plan was to use this same signal.

David: I gave it a virus. A computer virus.
General Grey: Are you telling us you can send out a signal that will disable all their shields?
David: Just as they used our satellites against us, we can use their own signal against them.

David: If we plant the virus directly into the mother ship, it would then filter down into all the corresponding ships below.
Nimziki: And just how do we infect the "Mother Ship" with a virus?
David: We'll have to fly their craft out of our atmosphere and dock with the mother ship. We can enter here, upload the virus and set off an explosion that could disable it. This would disorient the smaller ship below and buy you some time to take them out.
Nimziki: This is ridiculous.
General Grey: How long would their shields be down?
David: Once they discover the virus it could be a matter of minutes.

So what do we know

• The Harvesters technology is compatible enough that they could use out Satellites.
• The Harvesters signal interfered with our own, evident by the distorted TV signals everyone was getting.
• The Signal could be separated with our technology, as per David's suggestion before he realized what it really was.

David also had the previous research done by Area 51 who had one of the Harvesters' ships which crashed in Roswell about 50 years prior. When his Father gave him the idea for the Virus he wakes up one of the Area 51 Scientists. While it had been largely inactive they did repair it since and it did come alive recently and the time since the Harvesters first appeared they probably worked out if at the very least it's systems ran off a Binary System like our computers.

The fact that the ship alive when the Harvesters arrived was an indicator that the ship could probably still intact with the Harvesters other ships (one could assume that it came alive when the signal was first implanted). If you could infect that ship you could at the very least transmit the Virus from that Ship into the Mothership when the 2 connected since apart of the plan was to would disorient the smaller ships with the Mothership's destruction. To alter David's Joke about giving the Area 51 Ship a Cold, the Area 51 Ship could be used like a Patient Zero.

Don't forget how smart David is. Not only did he discover and learn the nature of the signal he got Constance's number, used her in use phone to triangulate her position inside the Whitehouse and guided her to a nearby window which he and his father could be seen from. He also anticipated the Virus being counteracted within a matter of minutes and volunteered for the mission thinking of what he might need to do if anything went wrong rather than making a 1-click install package for someone else

Constance's: With you? I don't understand why you can't just show someone how to plant the virus, somebody trained for this kind of mission?
David: If anything goes wrong I'll have to think quickly, adjust the signal, who knows?

I suspect that the Virus was a rush job so don't expect a well documented, well formatted piece of programming art

Script Sourced from Internet Movie Script Database

There are many things that make this exceedingly unlikely:

1. Are their computers even electronic? They could be light-based, they could be quantum computers, or for all we know they could run on water!
2. Do their computers use a wireless form of communication? If I recall correctly, he connected his computer to their wireless network to upload the virus. (If I'm mistaken, then this point is irrelevant, but the next point is not.)
3. If they have electronic computers with a wireless communication protocol, (or even a wired communication protocol), could we understand it? And if so, could we actually interface with it? Would our hardware be able to produce the frequencies and/or voltages necessary to send data over the air or over the wire?
4. Does the instruction set of their processor make any sense? Do they use the same sorts of math that we do?
5. If all the above objections are satisfied or ignored, wouldn't they have some sort of security to prevent such an attack vector?
6. Even if those things aren't a problem, would there have been enough time from the time the attacks started until the time they uploaded the virus to have figured it all out and implement it?

To play devil's advocate, you could argue:

1. Dr. Goldbloom (sorry, I forget the character's name) was a genius! Surely if anyone could figure out something like this, he could!
2. Our own governments and corporations can't secure their important data, why should we think that aliens would be any better at it than us?
3. When you're traveling through space, you don't run into a lot of other people (or whatever you want call other sentient species), so it makes sense to make everything as simple as possible. Who needs encryption when your nearest enemy is a primitive backwater planet 50,000 light years away?

Whatever you think about any of the above though, the point of a movie like this is to turn your brain off and have fun! Is it realistic? Not at all. Should it matter? Not at all! Independence Day was intended as a popcorn action flick. It wasn't supposed to be a realistic depiction of meeting aliens. If you want that (and it's worth seeking that out), go see Arrival. But if you're going to watch Independence Day (and it's worth watching!) turn your brain off and have a blast!

Well..., someone had already posted this question. Nonetheless these answers are very good. Thank you.

In the other question, one answer talked about deleted scenes that could explain something: " In a deleted scene, Goldblum mentions that he has deciphered their programming language and that the 50 year old Roswell ship is using the same programming language and operating system. So it's not a stretch to assume that he managed to write a rudimentary virus."
Also mentioned in this other article (second article in the list)