Yahoo's board of directors is scheduled to meet Wednesday, and besides hearing presentations from investment adviser Allen & Co., it's also under a new threat from Daniel Loeb's Third Point fund.

Last week, Third Point acquired a 5.2 stake in Yahoo after CEO Carol Bartz was fired. Now the New York-based fund indicated it wants to increase its shareholdings in a bid to oust chairman Roy Bostock and other Yahoo directors.

Yahoo shares rose about 2 percent to $14.56, after Third Point's disclosures. Loeb said lawyers will be filing legal forms to allow the hedge fund to purchase more Yahoo shares. He did not indicate how many more he wants to acquire.

Additionally, Loeb disclosed an acerbic conversation with Bostock and sent a letter to Yahoo co-founder and former CEO Jerry Yang. We urge you to do the right thing for all Yahoo shareholders and push for desperately needed leadership change, he wrote.

Loeb told Yang, We are prepared to support you and present you with leadership suggestions on candidates who could help bring Yahoo back to its rightful place.

Yang, with co-founder David Filo, is still the Sunnyvale, Calif.-based company's Chief Yahoo, as well as a major shareholder through various blind trusts. Both have sold Yahoo shares since the company's IPO.

Loeb previously shook up Massey Energy and acquired stakes in other companies. Activist investor Carl Icahn also acquired shares in Yahoo but left after Bartz came in as CEO in 2009.