The hacker group Anonymous is preparing a cyberattack on corporate sponsors of the World Cup in Brazil to protest against the lavish spending on soccer games in a country struggling to provide basic services, said a hacker with knowledge of the plan.
Earlier this week, Anonymous attacked the computer networks of Brazil's foreign ministry and leaked dozens of confidential e-mails.
"We have already conducted late-night tests to see which of the sites are more vulnerable," said the hacker who operates under the alias of Che Commodore. "We have a plan of attack."
"This time we are targeting the sponsors of the World Cup," he said in a Skype conversation from an undisclosed location in Brazil. Asked to name the potential targets he mentioned Adidas, Emirates, Coca-Cola and Budweiser, which is owned by Anheuser-Busch.
There was no way to confirm Che Commodore's identity or his affiliation with the group Anonymous.
The sponsors did not immediately respond to requests to comment on the threat.
A Distributed Denial-ofService (DDoS) is a low-cost attack aimed at taking a website offline by simultaneously requesting access from thousands of computers in order to jam the host server.
The threat of cyberattacks is yet another headache for the organisers of the World Cup kicking off on June 12. The 32-nation soccer tournament has already been marred by embarrassing delays in the building of stadiums and widespread discontent in Brazil over the excessive cost of hosting the event in a country with deficient public services.
In what could be the biggest cybersecurity breach since the US National Security Agency allegedly spied on President Dilma Rousseff's personal communications, Anonymous this week posted 333 documents extracted from the foreign ministry's computing network.
They include a briefing of talks between Brazilian officials and US Vice-President Joe Biden during a visit to Brazil in May last year and a list of sports ministers who plan to attend the World Cup.
A hacker known as AnonManifest used a phishing attack to break into the foreign ministry's databases and eventually access its documentation system, said Che Commodore.
"Until yesterday afternoon the hacker still had access to the system," he said.
The foreign ministry closed down its e-mail system after the attack and instructed its 3,000 e-mail account holders to change their passwords. Federal police are investigating the breach.
A foreign ministry official said that only 55 e-mail accounts were hacked and the only documents obtained were attached to e-mails and from the ministry's internal document archive.
"The problem has been resolved. Nothing important was leaked," said the official, who asked not to be identified because he was not authorised to discuss the matter.
But Brazilian diplomats abroad were left without e-mail communications with their headquarters for several days. One diplomat in a European capital said on Friday that the e-mail service was still down.