Malik b. Anas is not an author of Sihahus-Sitta. The term "Sihahus-Sitta" refers to the six most authentic collections of Hadith in Sunni Islam, and the authors are commonly known as the "Kutub al-Sittah" or the "Six Books". These six books are:
1. Sahih al-Bukhari, compiled by Imam Bukhari
2. Sahih Muslim, compiled by Muslim b. al-Hajjaj
3. Sunan Abu Dawud, compiled by Abu Dawud
4. Jami at-Tirmidhi, compiled by at-Tirmidhi
5. Sunan an-Nasa'i, compiled by an-Nasa'i
6. Sunan Ibn Majah, compiled by Ibn Majah
Malik b. Anas is the author of the Muwatta, which is also a collection of Hadith but is not considered one of the Sihahus-Sitta.