IBM plans to buy Internet Security Systems (ISS) for US$1.3 billion in a bid to bolster its IT security portfolio.

ISS, based in Atlanta, offers software, appliances and services that help companies protect their networks, desktops and servers from Internet threats.

IBM hopes the acquisition, due to be announced today, will help it better address growing concerns that companies have regarding various security issues such as data theft and compliance with government regulations.

Given ISS's high profile in the corporate sector, the deal would rank one of the most significant to have happened this year.

IBM plans to integrate ISS' software with its Tivoli IT service management portfolio and sell ISS' managed security services through its existing sales channels.

The company also plans to continue offering ISS's security intelligence service, which details global online vulnerabilities and threat conditions for enterprises. ISS operates security operations centres around the globe and IBM expects to add those to its existing centres.

ISS, which has 11,000 customers, will become a business unit within IBM Global Services' security organisation. The companies expect the deal to close in the fourth quarter of this year.