AOL has suggested customers create new passwords and security questions that may have been seized in a data breach April 22.
The company, which has stated it is currently researching the breach, is simultaneously working to ensure customers can safely browse the Internet, CBS Marketwatch reported.
"We are working closely with federal authorities to pursue this investigation to its resolution," the company said. "Our security team has put enhanced protective measures in place and we urge our users to take proactive steps to help ensure the security of their accounts."
According to CBS Marketwatch, hackers reportedly took AOL users' financial information, e-mail addresses, encrypted passwords, answers to security questions, postal addresses, and address book information. Security protection on users' passwords and security questions were reportedly not affected.
AOL began investigating the issue when the company started receiving more spam e-mails from company addresses than usual, CBS Marketwatch reported.
AOL also stated legitimate messages are normally sent directly from the sender or Internet service provider.
Violators typically change e-mail addresses so they look like they are legitimate and consumers open them. AOL will notify users of affected accounts.
Monday's AOL security breach was the second for an Internet company in two days. Hackers reportedly tried to surpass a security flaw in Microsoft's Internet Explorer versions six through 11 as a result of general security issues Monday.
Limited targeted attacks also occurred, in attempts to surpass the defect.
A spokesman for cyber security software company FireEye told Forbes the firm noticed a discrepancy, and is continuing to investigate the matter.
"It's unclear what the motives of this attack group are at this point. It appears to be broad-spectrum intel gathering," Vitor De Souza said.
