Yahoo's board is under attack, the latest headache for Marissa Mayer

When Marissa Mayer took over Yahoo in July 2012, she was the fifth CEO in five years to try her hand at resuscitating the once mighty Internet media and search site.

But after less than four years in, as she's been fighting against employee and user ennui, Mayer is now facing an energetic foe that wants the company to fire its entire board of directors and possibly part ways with the CEO.

If they're successful, that would give Yahoo six CEOs in less than 10 years, which may be a corporate record of sorts -- but probably not the one the company is going for.

An activist investor group called Starboard Value said in a letter to other Yahoo shareholders Thursday that it wants a new group of people to oversee a "turnaround plan, separation, or sale of assets" (PDF). Yahoo's current board includes Mayer and company co-founder David Filo.

"We believe that Yahoo is deeply undervalued and opportunities exist within the control of management and the Board of Directors to unlock significant value for the benefit of all shareholders," Starboard wrote in its letter. Though it didn't exactly say that it wants Mayer ousted as CEO, the group added that "we have been extremely disappointed with Yahoo's dismal financial performance, poor management execution, egregious compensation and hiring practices, and general lack of accountability and oversight by the Board."

A former Google executive, Mayer's been criticized for some of the efforts she's made to bring Yahoo back to relevance and keep it competitive with rivals including Facebook, Google and Snapchat. So Starboard has plenty of ammunition.

Mayer's missteps include Yahoo Screen, the company's premium video service, which was shut down in January. Yahoo admitted it couldn't find a way for the service to make money, even with the help of newly produced programming including a revival of the NBC cult comedy "Community." Yahoo admitted the slate of shows sucked up $42 million from its coffers.

Its messaging service Livetext, a video chat app (but with no sound) was shut down eight months after it launched. And eight of the top 10 smartphone apps in the United States in January are made by rivals Facebook and Google, according to Comscore. Yahoo's only spot on the top 15 is Apple's Stocks app for iPhones, powered by Yahoo's financial data.

Yahoo still has a large audience -- it claims 1 billion people visit all its sites combined each month. But it hasn't found ways to make that pay, and it hasn't been able to find sure footing with its products.

The misses have sunk employee morale, with key executives leaving and Mayer apparently asking the remaining leadership to make multiyear commitments to Yahoo. In February, Mayer unveiled her make or break plan for the company, including cutting 1,700 jobs. She also put out a call to would-be buyers, saying she and Yahoo's board are ready to "engage on qualified strategic proposals."

That "bold" plan, as Yahoo described it, isn't bold enough for Starboard.

"We believe the board clearly lacks the leadership, objectivity and perspective needed to make decisions that are in the best interests of shareholders," the group said in its letter. "The management team and Board of Yahoo have repeatedly failed shareholders."

Yahoo said its Nominating and Governance Committee will review the proposal and "respond in due course." Starboard didn't respond to a request for comment beyond its letter.

This isn't the first time Starboard has tried to force a company to clean house. In 2014, Darden Restaurants, the owner of Olive Garden and other chains, replaced its entire 12-person board after pressure from Starboard. As part of its campaign, Starboard published a presentation filled with embarrassing critiques of Olive Garden. A few of the jabs: "How does the largest Italian dining concept in the world not salt the water for pasta?" And, the fried lasagna bites were "barely edible."

Now Starboard is swapping unlimited salad and breadsticks for, well, whatever Yahoo is focusing on now.

Mayer has dealt with activist investors before. Daniel Loeb, of the hedge fund Third Point, was key to Mayer's hiring at Yahoo in the first place. But Mayer eventually forced him out because she wanted to ensure her control of the company. "She got him out," an industry executive told Vanity Fair in 2014. "Dan had a gun to her head whether she knew it or not, and she orchestrated his departure."

Starboard, which said it owns 1.7 percent of Yahoo, wants to nominate its nine board replacement candidates at Yahoo's annual shareholder meeting later this year. Those candidates include Jeffrey Smith, Starboard's CEO, and Eddy Hartenstein, chairman of Tribune publishing, which owns the Chicago Tribune, the Los Angeles Times and The Baltimore Sun.

"We cannot envision a scenario where the shareholders of Yahoo would entrust the current management team and Board with executing a standalone turnaround plan given the years of failed attempts under the current leadership," Starboard wrote.