Beginning in June 2011, hackers from Anonymous and LulzSec collaborated on a series of cyber attacks known as “Operation AntiSec”. On June 23, in retaliation for the passage of the immigration enforcement bill Arizona SB 1070, LulzSec released a cache of documents from the Arizona Department of Public Safety, including the personal information and home addresses of many law enforcement officers. On June 22, LulzSecBrazil took down the websites of the Government of Brazil and the President of Brazil. Later data dumps included the names, addresses, phone numbers, Internet passwords, and Social Security numbers of police officers in Arizona, Missouri, and Alabama. Antisec members also stole police officer credit card information to make donations to various causes.

On July 18, LulzSec hacked into and vandalized the website of British newspaper The Sun in response to a phone-hacking scandal. Other targets of AntiSec actions have included FBI contractor ManTech International, computer security firm Vanguard Defense Industries, and defense contractor Booz Allen Hamilton, releasing 90,000 military e-mail accounts and their passwords from the latter.

In December 2011, AntiSec member “sup_g” (alleged by the U.S. government to be Jeremy Hammond) and others hacked Stratfor, a U.S.-based intelligence company, vandalizing its web page and publishing 30,000 credit card numbers from its databases. AntiSec later released millions of the group’s e-mails to Wikileaks.