Thompson, 59, has led the Cupertino, California, security vendor for the past decade. He will be replaced by Enrique Salem, the company's chief operating officer, effective April 4, 2009, Symantec said in a statement released Monday afternoon.

During his tenure, Thompson built Symantec from a consumer desktop software vendor, best known for its Norton products, into a leading enterprise software provider. The company aggressively acquired new software companies including its most high-profile purchase: the 2005 US$10.5 billion acquisition of enterprise storage software vendor Veritas.

"He grew it from what was essentially a desktop software vendor to arguably the most important security pure-play," said Andrew Jaquith, a senior analyst with Forrester Research who formerly worked for Symantec under Thompson's leadership. "He's made a lot of gutsy calls; buying Veritas was an amazingly gutsy call, and it was the right one."

Investors might disagree with that assessment. Symantec's stock [SYMC] dropped on news of the Veritas merger four years ago and has never returned to its pre-acquisition highs.

Although Symantec has warned of a slowdown in sales recently, executives said Monday that they have been working on the transition for the past 10 months already, an effort called "Project Texas."