Cyber crime - internet banking and credit card fraud - is now the fastest growing sector of global organised crime, increasing at a rate of about 40% per year.
"Fabio" commits his crimes from the anonymity of a cyber cafe
With Brazil thought to have by far the largest number of cyber criminals, Misha Glenny, reporting for the BBC World Service's How Crime Took On The World, went to meet some of those trying to profit from the $100bn (£51bn) industry.
Fabio's small frame is hunched over an ancient computer screen in a dingy internet cafe in one of the favelas of Sao Paulo. He is learning the basic skills needed to commit crime online.
Fabio - not his real name - is taking his online lessons from experienced computer hackers. He is disarmingly matter-of-fact about his new career.
"I buy small things - mobile phones, cameras - so that people don't even know I've been using their credit cards," he explains.
Fabio is a low-level frontline operative in a rapidly expanding battle taking place in the virtual world. For the moment, he is unlikely to be caught because he is restricting himself to the regular theft of small amounts of money.
Fabio works on the rational principle that only a minority of credit card holders check their statements carefully.
Even if they did, they might think twice before reporting a minor theft to the police. And he also knows it is highly unlikely that the police will have the resources to pursue him.
Nonetheless, Fabio's modest assault on people's bank accounts is the tip of a very large iceberg - and one which is creating a headache for law enforcement agencies around the world.
Legal definition officially agreed in 2004
Worth over $100bn per year
Includes hacking - stealing data from other people's computers - and "phishing" - sending fake emails asking for bank details
Many cyber criminals operate out of developing nations
"The cost of identity theft and computer-based credit card fraud stood at $52.6 billion in 2005," says Peter Allor, boss of The X-Force, the cyber intelligence unit of leading cyber security firm IBM ISS.
Cyber crime's turnover has been growing rapidly ever since, so that now estimates of its value stand at that huge $100 billion figure annually.
But banks and other major companies are reluctant to release any figures about the losses they sustain, for fear of scaring off customers. That is why they continue to reimburse the victims of computer scams with no questions asked.
Fabio's descent into the world of cyber crime began recently. He has never had a fixed job which paid well, and struggles to get by - he is divorced and travels two hours by bus to Sao Paulo in order to support his one son.
Poverty and destitution - common in the favelas of Sao Paulo, Rio de Janeiro and other Brazilian cities - have certainly contributed to his determination to make money from cyber crime.
Fabio is one of only a tiny minority of young people in Brazil who use computers to commit crime. But there are concerns that, as thousands more become web literate, there will be an exponential rise in cyber crime.
Access to the web is easy thanks to the cheap internet cafes studded around the suburbs of Brazil's economic hubs - where most young people use them to play games or educate themselves.
Fabio is defensive when I suggest to him that crime on the internet is wrong - however poor he is.
"I'm not trying to rob anyone who wakes up early in the morning and takes the bus, and has to get home and feed his kids, and doesn't have money," he insists.
And he tells me his ultimate aim is to befriend a very rich person online - "someone who owns a limo or a helicopter and who doesn't care about poor people". He is convinced that he will be able to milk his victim for a serious amount of money.
For the moment, however, Fabio is small fry.
Brazil's new federal cyber police force in the capital Brasilia is constantly battling against large-scale scams originating in the country.
Hackers send out millions of spam emails to addresses across the world every day, and a small percentage of computer users are gullible enough to answer them.
Bank account numbers and passwords are then handed over unknowingly to unscrupulous cyber crooks.
There is no way to protect yourself 100% from Fabio and his friends.
But you can minimise the risk. Always keep anti-malware - programmes which prevent the installation of malicious programmes on your system - and anti-virus software up-to-date; never answer an email if its origin is unclear.
And if anybody offers you free sex, stay well clear of that - you could end up with a nasty infection.
Misha Glenny is the author of McMafia: A Journey Through the Global Criminal Underworld.