The NCSC-TG-025 standard of the National Computer Security Center is a common method of data destruction. The method causes a software-based three-time overwriting of existing information on a data medium.
The technical function of the NCSC-TG-025 is to be portrayed as follows:
Pass 1: Overwriting the data with a zero as well as verifying the writing of this character;
Pass 2: Overwriting the data with a one and verifying the writing of this character;
Pass 3: Overwriting the data with a random character as well as verifying the writing of this character.
The NCSC-TG-025-Erasure Method is equivalent to the Method of the United States Department of Defense (DoD 5220.22-M).
After erasure of a hard disk with help of the NCSC-TG-025 method, software-based restoration of the data is generally not possible. The extraction of data via hardware-based methods is largely excluded.
The NCSC-TG-025 procedure was originally published and defined in the Forest Green Book by the National Computer Security Center (NCSC), originally a part of the US National Security Agency (NSA).