A string of smaller Chinese companies, such as Renren, 21Vianet Group and E-House China Holdings, have all received "go-private" bids in recent weeks.
Tech executives at several Chinese companies are betting on higher valuations back home, where stock markets have been on fire for some time.
China's ChiNext composite index has soared 156.6 percent so far this year, eclipsing the 27 percent rise in the Nasdaq OMX China Technology Index.
Many of these companies also hope to avoid any legal fallout when Beijing formally outlaws foreign shareholder control of firms in protected tech sectors.
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Other Chinese firms on the "go-private" bandwagon include Shanda Games and Perfect World, which have already agreed to be taken private, while online dating service Jiayuan.com and medical R&D services provider WuXi PharmaTech said they are considering it.
Qihoo, whose flagship product was used by 778 million smartphone users, said its board would form a committee to evaluate the offer of $77 per American depositary share (ADS), or $51.33 per ordinary share.
The offer is at a 16.6 percent premium to the stock's Tuesday close of $66.05, valuing Qihoo at about $10.06 billion based on its outstanding shares as of March 31.
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The company's U.S.-listed shares rose 8 percent to $71.35 on Wednesday.
Qihoo's market capitalization did not show its full value, and privatization is "what we must do to bring out the company's worth," Forbes quoted Zhou as saying in an internal e-mail.
Zhou, who is also Qihoo's co-founder, served as chief executive of Yahoo's China unit from January 2004 to August 2005.
Up to Tuesday's close, Qihoo's shares had risen more than 15 percent this year.