We all know that cloud computing, essentially Internet-based computing and storage -- is an important initiatve for tech's big hitters like Microsoft ( MSFT) and IBM ( IBM). But greater adoption of the cloud will come only as customers are reassured that cloud computing -- which entails external management of secure data, services and information -- is secure. Cloud security, a burgeoning market, is set to open up a major revenue stream for Silicon Valley. Forrester estimates that the cloud security market could be worth $1.5 billion by 2015. Driving this subset of the cloud market is HP, which last year unveiled Cloud Assure, a mixture of software and services focused on ensuring that cloud-based data is not compromised. Rival IBM is also getting in on the act, and is heavily involved in the European Union's Trustworthy Clouds project. Service providers will also turn to traditional security technologies from Symantec ( SYMC) and Intel's ( INTC) McAfee ( MFE) to protect their clouds, said Richard Wang, a manager at security research specialist SophosLabs. "It's going to be a lot about intrusion prevention, data loss prevention and encryption. "I think that cloud security is going to come to the fore." "This is a big deal," said David Gee, HP's vice president of worldwide marketing. "You want to be able to design and test, not just for quality and performance of an application in the cloud, but also for security and potential defects."