A phishing email scam has forced data storage firm Seagate Technology to disclose private employee information.

Tax information, including Social Security numbers and salaries, for all current and former U.S.-based employees was sent to an unauthorized third party last week, the Cupertino-based company told CNBC in an e-mailed statement.

"The information was sent by an employee who believed the phishing email was a legitimate internal company request...At this point, we have no information to suggest that employee data has been misused, but caution and vigilance are in order."

Seagate added that it had immediately notified the Internal Revenue Service (IRS), which is now actively investigating it along with federal law enforcement.

Seagate also provided affected employees with a two-year membership to an identity theft protection service developed by Experian.