T1027.011: Fileless Storage

Adversaries may store data in "fileless" formats to conceal malicious activity from defenses. Fileless storage can be broadly defined as any format other than a file. Common examples of non-volatile fileless storage include the Windows Registry, event logs, or WMI repository.

Similar to fileless in-memory behaviors such as Reflective Code Loading and Process Injection, fileless data storage may remain undetected by anti-virus and other endpoint security tools that can only access specific file formats from disk storage.

Adversaries may use fileless storage to conceal various types of stored data, including payloads/shellcode (potentially being used as part of Persistence) and collected data not yet exfiltrated from the victim (e.g., Local Data Staging). Adversaries also often encrypt, encode, splice, or otherwise obfuscate this fileless data when stored.

Some forms of fileless storage activity may indirectly create artifacts in the file system, but in central and otherwise difficult to inspect formats such as the WMI (e.g., %SystemRoot%\System32\Wbem\Repository) or Registry (e.g., %SystemRoot%\System32\Config) physical files.

Detection

IDDS0005Data source and componentWMI: WMI CreationDescription

Monitor for the creation of WMI Objects and values that may highlight storage of malicious data such as commands or payloads.

IDDS0024Data source and componentWindows Registry: Windows Registry Key CreationDescription

Monitor for the creation of Registry values that may highlight storage of malicious data such as commands or payloads.

Mitigation

IDM1047NameAuditDescription

Consider periodic review of common fileless storage locations (such as the Registry or WMI repository) to potentially identify abnormal and malicious data.