RATINGS CHANGES

BHP Billiton (BBL) was downgraded to hold from buy at Jefferies. This was a valuation call, as the company lacks near-term catalysts, Jefferies said.

CBS (CBS - Get Report) was upgraded to outperform at Wells Fargo. There is a positive bias toward broadcast names, said Wells Fargo, and the investor day on March 15 should be a catalyst.

FireEye (FEYE - Get Report) was upgraded to overweight from neutral at Piper Jaffray. $24 price target. The path to profitability is clearer, said Piper Jaffray.

Frontier (FTR - Get Report) was downgraded to sell from neutral at Citigroup. $4 price target. The company is increasing leverage and may need to cut its dividend, Citi said.

Keysight (KEYS - Get Report) was downgraded to sell at Goldman Sachs. This was a valuation call, based on a $24 price target, said Goldman Sachs.

Nielsen (NLSN - Get Report) was downgraded to equal weight at Morgan Stanley. This was a valuation call, based on a $52 price target, Morgan Stanley said.

Shake Shack (SHAK - Get Report) was initiated with a sell rating at TheStreet Ratings.

Under Armour (UA - Get Report) was upgraded to buy at TheStreet Ratings. 

This article was written by a staff member of TheStreet.