More than 82 million FireEye shares can be traded for the first time on Wednesday without restrictions put in place after the company's secondary stock offering earlier this year.
The stock was up 9.78% to $31.76 at 12:21 p.m.
Analysts suggest the massive hacking attack won't trigger a "material adverse effect" clause that would threaten the acquisition.
FireEye (FEYE) stock continued to advance on Friday after Yahoo! verified a massive data breach yesterday.