Anonymous has compromised Twitter, the company’s largest service, and YouTube, the world’s largest video site, the group’s director of operations, Aaron Fawcett, told reporters.
The hacktivist group posted the credentials of Twitter users who use the social network, which allows them to post content on the site.
The breach was the first time it has been publicly known that Twitter has been hacked, he said.
Twitter is owned by Twitter Inc., which also owns Instagram, Pinterest, Spotify, Google+ and Twitter.
The group had previously compromised Twitter accounts for more than 30,000 employees, according to the group.
It has also gained access to LinkedIn accounts for nearly 40,000 companies, and Facebook accounts for about 25,000 accounts.
The hackers used an exploit on an exploit kit developed by Russian hackers to gain access to Twitter’s login system and the account passwords for some 2 million Twitter users.
It also stole login information for 2 million Facebook accounts.
Twitter has said it has patched the security holes.
Fawcetts told reporters Twitter has had a lot of users affected by the breach.
“It’s been an extremely frustrating experience,” he said, declining to provide further details.
Twitter said in a statement that it had not been notified of any specific breach.
Fawciett did not say whether Twitter had a timeline for responding to the breach, saying that “the time frame we provide for our response to the reports is not the same as the time frame for responding internally to a cyberattack.”
Twitter has faced scrutiny over the last few months over the security of the site and its role in the national security.
In July, a series by hackers with the hacker collective Anonymous exposed the personal information of more than 70 million people and more than 10 million accounts on the service, including more than a dozen accounts for Vice President Joe Biden.
Twitter had also received numerous reports about accounts belonging to Russian hackers and other groups.
The company has said that a separate breach involving more than 500,000 user accounts exposed the social media platform’s login information.
The Twitter group has been blamed for a string of other hacks, including an attempt to compromise LinkedIn accounts, and the breach of Microsoft’s personal information in March.
The hacks were widely believed to have been carried out by the group Anonymous, which has been active for years, using the online platform to spread propaganda.
Anonymous, also known as Anonymous, is a loosely organized collection of hackers and online activists who claim to be motivated by a variety of causes, including social justice and antisecrecy.