The Sony software, found on several of the company's recent albums, is triggered by playing one of the CDs in a PC. From the CD drive, the software installs itself deeply inside a hard drive and hides itself from view. This cloaking technique could be used by virus writers to hide their own malicious software, security experts have said. There is a range of opinion among security companies about how much risk the software poses, from those who consider it no worse than an adware pest to those who view it as potentially dangerous spyware.