Intel Corp. agreed to sell a majority stake in its computer-security unit to private-equity firm TPG, partly reversing a five-year-old acquisition that has largely proved disappointing.

TPG will take a 51% stake in the business in a deal that values it at $4.2 billion including debt, Intel said in a statement Wednesday confirming an earlier report in The Wall Street Journal. The business, recently called Intel Security, will use the McAfee name originally associated with it.

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