CORRECTED - IBM senior security executive Noonan retires

(Corrects second paragraph to show that IBM paid $1.3 billion for Internet Security Systems. Corrects fourth paragraph to show that Rahmani has worked for IBM for more than 20 years and was running a business that sells consulting, systems integration, software, hardware and security products.)

BOSTON, March 24 (Reuters) - An architect of IBM's security strategy retired last month after helping draw up a plan to invest $1.5 billion to expand that business this year, a company spokesman said on Monday.

Thomas Noonan, 47, general manager of International Business Machines Corp (IBM.N: Quote, Profile, Research) Internet Security Systems, joined the company in October 2006, after selling Internet Security Systems to IBM for $1.3 billion. He had been chief executive of ISS.

Internet Security Systems sells software and services that help companies keep attackers from breaking into corporate computer systems. It is also the business unit where IBM formulates security strategy for the rest of the company.

Val Rahmani - who has worked for IBM for more than 20 years and was running a business that sells consulting, systems integration, software, hardware and security products - was named as Noonan's replacement.

"Tom has gotten ISS absolutely centered as a key hub of our security strategy," said IBM spokesman Jim Larkin. "Now with Val, we'll keep that going."

IBM's technology services division, the world's largest, has long sold security products - mostly from other companies. Since it acquired ISS, it has been looking to expand its own line of IBM-branded services and software.

Rahmani said in a November interview that IBM was looking at "at a lot" of potential security companies that it might acquire.

She declined to say if it would pursue another deal as large as Internet Security Systems.

IBM already has "pretty good coverage (in security) but we could always do better," she said at the time. (Reporting by Jim Finkle, editing by Leslie Gevirtz)