It does seem really impressive a lot of the time but yeah - most things seen in films are really just fiction. Nothing more, and they'd never work in real life for about a million reasons!
If you want a truthful film, check out freedom downtime. It follows the story of Kevin Mitnick and a few of his friends trying to raise awareness of his story - sad in a way and not your typical action blockbuster at all, but a good watch with some funny moments. If you want to see what your typical hacker is really like, then that's what you should be looking at!
While I'm at it, here's what NOT to do:
1) Google for various programs that launch viruses, password crackers, common exploits, SQL injections and suchlike
2) Find a target PC
3) Run such programs on a target PC
This won't teach you anything, and will most likely do any of 2 things:
1) Get you a reputation as a mindless script kiddie
2) Get you in a lot of serious trouble generally
So yeah - there is that easy route, but it lands a lot of people in hot water and doesn't teach you anything, so steer clear of that one ;-)
Rather than watch films though, if you're interested in computer security there's a few things you can do that'll really help you:
1) Learn maths to a good standard. Especially integer mathematics (the branch that deals with whole numbers) and proof. Encryption stuff is very heavily maths based and you need a good knowledge to understand it all.
2) Increase your programming knowledge. Seriously, you can never go too far with this one, and it helps not just for the security side of things but pretty much everything else as well.
3) Buy a good book on some of the existing algorithms out there, learn how they're formed, their strengths and weaknesses and so on. To do this properly you'll need a good grounding in both of the above!
That is a very long route but the one that will ultimately give you the most knowledge on the subject. From there, learning about things like SQL injections and XSS would be pretty easy!
If you're after a shorter route but still want to learn something worthwhile I can recommend "how to break web software", it's a pretty comprehensive book covering most of the common web security flaws (and a pretty much essential read if you're doing any web stuff yourself that requires heightened security.)
Good luck with it if you're still interested, but remember computer security is a massive topic and one that's generally speaking not at all like what you see in some film!
