The Brazilian football federation says hackers momentarily took down its website.
The federation said that although the site was quickly restored, it remained unstable for some time while technicians worked on it.
Federation spokesman Rodrigo Paiva said before a press conference that the "site is a little slow because it has been under attack."
The federation said technicians were still trying to identify those responsible for the attack.
Paiva didn't think the attack was related to the national team's performance in the World Cup.
The federation said extra measures had been put in place to avoid hacker attacks on its site during the World Cup.