Hacker group Anonymous Brazil have started an online drive to disrupt local state websites and sponsors of the 2014 FIFA World Cup, according to online reports.
ITV.com in the UK reported that the group have defaced and brought down a number of websites, including Brazilian government agencies and attacked top FIFA partner sites, such as car manufacturers Hyundai.
The hackers have used what are known as DDoS attacks, causing sites to crash, and say they want the government to respect the people's needs. They have also defacement a number of Brazilian government sites.
"We had a busy last few days and there is more still to come," a hacker who calls himself Che Commodore and who claims to be a member of the Anonymous hacker collective told Reuters at the weekend.
“Companies and institutions that work with a government that denies the basic rights of its people in order to promote a private, exclusive and corrupt sports event will be targeted," he said, declining to give his real name.
Reuters reported that experts have warned about Brazil's lack of infrastructure and awareness to withstand computer attacks.
The web site of the government of Mato Grosso state, where Chile played against Australia on Friday, came under attack, an official said.
"Our site was hacked," said Daniele Cunha, a spokeswoman for the local government. "We were able to take it off the air and restore the service within 30 minutes."
Hackers last month broke into the foreign ministry's email service, accessing dozens of classified documents including a list of foreign dignitaries planning to attend World Cup matches.
A spokesman for Brazil's defence ministry said they have detected an "increase in hacker activism," but no attacks on federal government sites have been reported so far.
A loosely-knitted hacker network this week posted a list of 27 websites they claimed to have attacked but many of these have been denied.