The only entrance requirements for becoming a hacker are an inquiring mind and plenty of time. These are things that young teenagers - especially, though not exclusively, boys - tend to have.
The classic - and outdated - picture of the hacker is of a teen sitting in his bedroom, obsessively coding something impenetrable on his own, waiting to unleash a terrible virus that will wreak havoc on computers around the world.

In fact modern hackers are a gregarious bunch, who have grown up in a world where instant messaging and video chatting makes it possible to be connected to people at all times.
Hacker conferences are often friendly events: Eric Corley, published of the hacker underground 2600 magazine (who styles himself Emmanuel Goldstein, after the figure of hate in Nineteen Eighty-Four), is a watchful but otherwise outgoing person. Conferences tend to be fun affairs, with people showing off their latest hacks.
The initial lure of hacking – getting past the security hurdles on computers that are intended to turn the vast majority of people away – is simply the achievement. There's also the attraction of the fact that machines will do what you tell them, without argument, again and again. Once mastered, it's a delicious power.
Hacking knows no national boundaries: China, the former Soviet states and eastern Europe all have produced dangerously effective hackers. The US, Germany and Britain do so as well. Some of the better hackers may be persuaded to work for governments. The suspicion is that in China the most successful are given no option.
Hacking is possible because modern computer systems are so complex that there will always be a flaw to be exploited somewhere.
The web offers hackers a bell curve of targets: most are fairly secure, some are very secure, but there's a long tail of sites running outdated software that can be exploited.
Roughly half of the world is using Microsoft's Windows XP, which is 10 years old and – in its original form – riddled with security holes. Many of the copies used in the far east are pirated, and Microsoft refuses to let them be updated, which leaves the holes "unpatched".
This is meat and drink to hackers, who can often call on widely distributed "hacking kits" that let would-be "l33t haX0rs" (elite hackers) target sites by clicking a few buttons.
Many start their hacking career by breaking into websites to deface them; this is regarded by their elders as the lowest form of hacking (getting caught is even lower).
The more time they spend doing it, the sooner they realise that a certain level of skills will make it possible to make money, either by stealing credit card details and using them to buy virtual goods, or by getting paid to create "malware" that others will pay for.
That might be programs that will silently take over a computer, or subvert a web browser so it goes to a particular site for which they get paid, or lace a website with commercial spam.
That is where the road forks. The commercial hackers do not go to conferences, and keep out of the public eye as far as possible, which can be hard when you are making serious money from it.
They are the ones who the security and police services try very hard to keep their eyes on by any means possible, including infiltration and coercion.