Neustar, which helps telephone carriers route calls and text messages, said it would be taken private by an investment group led by private equity firm Golden Gate Capital in a deal valued at about $2.9 billion, including debt.
Neustar's shares were up about 20% at $33.30 in premarket trading on Wednesday, slightly below the offer price of $33.50 per share.
The equity value of the all-cash deal is about $1.85 billion, Neustar said.
San Francisco-based Golden Gate Capital had a stake of about 2.4 million shares in Neustar as of Sept. 30, according to a regulatory filing.
An affiliate of Singapore's sovereign wealth fund GIC Private will also make an investment and become a minority owner in Neustar, which was formerly a part of Lockheed Martin.
Neustar said in June it planned to split into two publicly traded companies, with one focusing on call routing services for telecom carriers and the other on marketing and security services.
J.P. Morgan Securities LLC provided financial advice to Neustar while Goodwin Procter and Wiley Rein acted as its legal advisers.
Golden Gate Capital's financial adviser was BofA Merrill Lynch while Kirkland & Ellis and Nob Hill Law Group provided legal advice.