In 2003, proprietary UNIX vendor SCO filed a $1 billion lawsuit against IBM. SCO accused IBM of surreptitiously incorporating proprietary UNIX source code into the open-source Linux kernel, thus infringing upon UNIX copyrights allegedly held by SCO. Although SCO initially declined to provide evidence of infringement, the company attempted to justify its suit by claiming that it would be technologically impossible for IBM to make Linux a suitable platform for businesses without misappropriating some UNIX intellectual property in the process.