of the software techniques were effective for sanitizing individual files. These included well-known algorithms such as the Gutmann method, US DoD 5220.22-M, RCMP TSSIT OPS-II, Schneier 7 Pass, and Secure Empty Trash on macOS (a feature included in versions OS X 10.3-10.9). The TRIM feature in many SSD devices, if properly implemented, will eventually erase data after it is deleted , but the process can take some time, typically several minutes. Many older operating systems do not support this feature, and not all combinations of drives and operating systems work. Data in RAM Data remanence has been observed in static random-access memory (SRAM), which is typically considered volatile (i.e., the contents degrade with loss of external power). In one study, data retention was observed even at room temperature. Data remanence has also been observed in dynamic random-access memory (DRAM). Modern DRAM chips have a built-in self-refresh module, as they not only require a power supply to retain data, but must also be periodically refreshed to prevent their data contents from fading away from the capacitors in their integrated circuits. A study found data remanence in DRAM with data retention of seconds to minutes at room temperature and “a full week without refresh when cooled with liquid nitrogen.” The study authors were able to use a cold boot attack to recover cryptographic keys for several popular full disk encryption systems, including Microsoft BitLocker, Apple FileVault, dm-crypt for Linux, and TrueCrypt. Despite some memory degradation, authors of the above described study were able to take advantage of redundancy in the way keys are stored after they have been expanded for efficient use, such as in key scheduling. The authors recommend that computers be powered down, rather than be left in a “sleep” state, when not in physical control of the owner. In some cases, such as certain modes of the software program BitLocker, the authors recommend that a boot password or a key on a removable USB device be used. TRESOR is a kernel patch for Linux specifically intended to prevent cold boot attacks on RAM by ensuring that encryption keys are not accessible from user space and are stored in the CPU rather system RAM whenever possible. Newer versions of the disk encryption software VeraCrypt can encrypt in-RAM keys and passwords on 64-bit Windows. Standards Australia ASD ISM 2014, Australian Government Information Security Manual, 2014 Canada RCMP B2-002, IT Media Overwrite