Zamknięty temat and other 65,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
This icon is a circular speech bubble, with a curved point at its bottom coming from the bottom left. Inside the speech bubble is an icon of a lock, which is a small rectangle with a hole in the middle and a curved line on top.