Satellite photos reveal the extent of Amazonian deforestation
Hackers have helped logging firms in Brazil evade limits on tree felling, says a Greenpeace report.
The hi-tech criminals penetrated a computer system designed to monitor logging in the Brazilian state of Para.
Once inside the system, hackers issued fake permits so loggers could cut down far more timber than environmental officials were prepared to allow.
Greenpeace estimates that 1.7m cubic metres of illegal timber may have been removed with the aid of the hackers.
Drawing on information released by Brazilian federal prosecutor Daniel Avelino, Greenpeace believes hackers were employed by 107 logging and charcoal companies.
"Almost half of the companies involved in this scam have other law suits pending for environmental crimes or the use of slave labour," said Mr Avelino in a statement issued by Greenpeace.
Mr Avelino is suing the companies behind the mass hack attack for two billion reals (£564m) - the estimated value of the timber illegally sold.
The Brazilian investigation of the hackers began in April 2007 and more than 30 ring leaders were arrested during the summer of that year. The ongoing investigation means that now 202 people face charges for their involvement in the subversion of the logging system.
The hack was made possible by a decision in 2006 to do away with paper forms to help monitor whether logging and charcoal firms were keeping to the quotas they were set.
Instead, the Amazon state of Para turned to a fully-computerised system that issued travel permits for the timber logging firms were removing. The intent was that travel permits would stop being issued once logging companies had reached their annual quota.
With the help of the hackers, Brazilian logging firms were able to issue fake permits allowing them to bust through these caps.
"We've pointed out before that this method of controlling the transport of timber was subject to fraud," said Andre Muggiati, Greenpeace campaigner in Manaus. "And this is only the tip of the iceberg, because the same computer system is also used in two other Brazilian states."