This icon is a part of a collection of Siatka aktywności Hashtag flat icons produced by Icons8. Icons follow the guidelines of iOS, Windows, and Android and are designed by a single designer, guaranteeing the consistent quality. Both PNG and vector are available.
It's a logo on many small rectangles in a grid pattern. It should be four by four but in the lower left of the image the last rectangles of the lower two rows and half of the third rectangles of the lower two rows are covered by blank space and a hashtag image.