Richard Stallman Quotes
Proprietary software tends to have malicious features. The point is with a proprietary program, when the users don't have the source code, we can never tell. So you must consider every proprietary program as potential malware.
Stallman, Richard. "Proprietary Software Is Often Malware." GNU.org, Free Software Foundation, 2013.
Richard Matthew Stallman, also known by his initials, rms, is an American free software movement activist and programmer. He campaigns for software to be distributed in a manner such that its users receive the freedoms to use, study, distribute, and modify that software. Software that ensures these freedoms is termed free software. Stallman launched the GNU Project, founded the Free Software Foundation, developed the GNU Compiler Collection and GNU Emacs, and wrote the GNU General Public License.