Hackers broke into the website of Brazil's statistics agency early on Friday, the latest in a string of attacks against government sites this week.
The IBGE statistics agency took its website offline after the attack and said the hackers did not gain access to its research databases.
Hackers replaced the opening page of the site with a notice splashed with an eye altered in the colors of the Brazilian flag.
This month, the government will see the biggest number of virtual attacks in history by Fail Shell. Understand these attacks as a protest by a nationalist group that wants to make Brazil better. Be proud of being Brazilian, love your country; only this way can we grow and evolve! the notice read.
The note was signed FIREH4CK3R.
The IBGE reassures that research databases are intact and were not reached in the hacker attack, the agency said in an emailed statement.
A number of Brazilian government sites have been attacked this week, including the presidency and the Sports Ministry.
The hacking group known as LulzSecBrazil also released what it called personal data on President Dilma Rousseff and Gilberto Kassab, the mayor of Sao Paulo, on Thursday.
LulzSec has made widely publicized assaults on Sony Corp, the CIA, News Corp's Fox TV and other targets. The attacks have mostly resulted in temporary disruptions to websites and the release of user credentials.
LulzSec said on Monday in a Twitter message that it was seeking to hack government websites to leak classified government information.
The IBGE hackers took a shot at LulzSec, saying on the site's replaced opening page: There's no room for groups without an ideology such as LulzSec or Anonymous in Brazil.
(Reporting by Maria Pia Palermo; writing by Luciana Lopez; editing by Mohammad Zargham)