(Reuters) - Activist investor Mantle Ridge has built up a stake of over $1 billion in consultancy firm Cognizant Technology and believes its shares are undervalued, the Wall Street Journal reported on Friday.

Shares of the company rose nearly 4% in extended trading.

The activist firm has been privately engaging with Cognizant about its progress on boosting the share price, the report said, citing people familiar with the matter.

Mantle Ridge started buying up shares of the company in the second half of 2022, when the stock was trading in the high $50 to low $60 per share range, the report added.

Cognizant did not immediately respond to a Reuters request for comment.