Following what appears to be the preliminary stages of the investigation into the Wednesday incident, Twitter revealed that they had "detected what we believe to be a coordinated social engineering attack by people who successfully targeted some of our employees with access to internal systems and tools".
In a series of tweets, the company said that this access was used to "take control of many highly-visible (including verified) accounts and Tweet on their behalf", noting that they are looking into "what other malicious activity they may have conducted or information they may have accessed".
According to Twitter, the limitation of functionality of a "much larger group of accounts, like all verified accounts (even those with no evidence of being compromised)" was "disruptive,.. but an important step to reduce risk".
The company stressed that access to the compromised accounts will be restored to their original owners "only when we are certain we can do so securely", noting that "significant steps" have been taken to limit access to internal systems and tools while the investigation continues.
"Internally, we’ve taken significant steps to limit access to internal systems and tools while our investigation is ongoing. More updates to come as our investigation continues", the company statement said.
Earlier, Twitter CEO Jack Dorsey, commenting on the attack, pledged to share more information on the incident as soon as the company reaches a "more complete understanding" of what happened.
Twitter launched its investigation after it was rocked by a massive hacker attack on Wednesday that pulled a large number of users, including prominent verified accounts, into a bitcoin scam. Among those affected were the accounts of big companies, such as Apple and Uber, and public figures such as Elon Musk, Bill Gates, Jeff Bezos, Kanye West, Joe Biden, Barack Obama, Mike Bloomberg and many others.