The purchase would make IBM a one-stop shop for enterprise security needs, said Paul Stamp, an analyst at Cambridge, Mass.-based Forrester Research Inc. "It will give them arguably the broadest security suite" among vendors, he said.

The move represents an evolution in thinking at IBM, said Pete Lindstrom, an analyst at Spire Security LLC in Malvern, Pa. After studiously staying away from network security products for several years, IBM appears to be changing course a bit with this purchase, he said.

"IBM hasn't expressed much interest in this active [network] monitoring space," choosing instead to focus on identity and access management technologies, he said. "I guess they couldn't ignore the growth in this market," he added.

John Pescatore, an analyst at Stamford, Conn.-based Gartner Inc., said that parts of ISS's business make sense for IBM -- while others do not.

"IBM acquiring the managed services part of ISS makes sense," Pescatore said. "ISS did a pretty good job of it" and has been holding on to its share of the overall market for some time. Acquiring that portion of ISS's business should help IBM considerably bolster its own capabilities in the market, he said.