US technology company IBM's acquisition spree shows no signs of slowing down with a $1.3bn (€1bn) acquisition this week of an internet security firm. It is Big Blue's fourth buyout this month.

IBM has acquired Internet Security Systems, which provides security for networks and protects them from online attacks, for $1.3bn in cash. IBM has made 10 acquisitions this year according to Dealogic, the investment banking research provider.