Hackers associating themselves with the Anonymous collective have threatened to disrupt this summer's World Cup in Brazil.
The eight billion pounds spent on the games despite widespread poverty in the country has fuelled resentment towards the government and already caused street protests in major cities.
Cyber-sabotage could pose a serious problem to a tournament already marred by over-spending and worries about physical security issues.
Rio de Janeiro where some of the matches will be held
Activists have threatened to target Fifa, the Brazilian government and sponsors.
Another activist known as Che Commodore said the attacks will be distributed denial of service attacks - those designed to flood a website with requests until it crashes.
He added: "It's fast, damaging and relatively simple to carry out."
There are worries that not enough attention has been paid to cyber threats in Brazil and the country's ageing telecommunications infrastructure only adds to the problem.