T1027.011 Fileless Storage — Attack Pattern

Description

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 in Windows systems include the Windows Registry, event logs, or WMI repository.(Citation: Microsoft Fileless)(Citation: SecureList Fileless) Shared memory directories on Linux systems (`/dev/shm`, `/run/shm`, `/var/run`, and `/var/lock`) and volatile directories on Network Devices (`/tmp` and `/volatile`) may also be considered fileless storage, as files written to these directories are mapped directly to RAM and not stored on the disk.(Citation: Elastic Binary Executed from Shared Memory Directory)(Citation: Akami Frog4Shell 2024)(Citation: Aquasec Muhstik Malware 2024)(Citation: Bitsight 7777 Botnet)(Citation: CISCO Nexus 900 Config). Similar to fileless in-memory behaviors such as Reflective Code Loading and Process Injection, fileless data storage may remain undetected by antivirus and other endpoint security tools that can only access specific file formats from disk storage. Leveraging fileless storage may also allow adversaries to bypass the protections offered by read-only file systems in Linux.(Citation: Sysdig Fileless Malware 23022) 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.(Citation: Microsoft Fileless)

MITRE ATT&CK Detection Strategies
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DET0344 Detection Strategy for Fileless Storage via Registry, WMI, and Shared Memory

AN0973 Windows

Detects abuse of fileless storage mechanisms such as Registry keys, WMI classes, and Event Logs used to stage payloads, scripts, or encoded content outside traditional files.

WinEventLog:Security WinEventLog:Application

AN0974 Linux

Detects usage of shared memory directories (/dev/shm, /run/shm) for temporary storage of obfuscated, encoded, or executable data without persistence to disk.

auditd:SYSCALL linux:osquery

MITRE ATT&CK Mitigations
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M1047

Audit

Auditing is the process of recording activity and systematically reviewing and analyzing the activity and system configurations. The primary purpose of auditing is to detect anomalies and identify potential threats or weaknesses in the environment. Proper auditing configurations can also help to meet compliance requirements. The process of auditing encompasses regular analysis of user behaviors and system logs in support of proactive security measures. Auditing is applicable to all systems used within an organization, from the front door of a building to accessing a file on a fileserver. It is considered more critical for regulated industries such as, healthcare, finance and government where compliance requirements demand stringent tracking of user and system activates.This mitigation can be implemented through the following measures: System Audit: - Use Case: Regularly assess system configurations to ensure compliance with organizational security policies. - Implementation: Use tools to scan for deviations from established benchmarks. Permission Audits: - Use Case: Review file and folder permissions to minimize the risk of unauthorized access or privilege escalation. - Implementation: Run access reviews to identify users or groups with excessive permissions. Software Audits: - Use Case: Identify outdated, unsupported, or insecure software that could serve as an attack vector. - Implementation: Use inventory and vulnerability scanning tools to detect outdated versions and recommend secure alternatives. Configuration Audits: - Use Case: Evaluate system and network configurations to ensure secure settings (e.g., disabled SMBv1, enabled MFA). - Implementation: Implement automated configuration scanning tools like SCAP (Security Content Automation Protocol) to identify non-compliant systems. Network Audits: - Use Case: Examine network traffic, firewall rules, and endpoint communications to identify unauthorized or insecure connections. - Implementation: Utilize tools such as Wireshark, or Zeek to monitor and log suspicious network behavior.

Fileless Storage

Description

MITRE ATT&CK Detection Strategies 1

MITRE ATT&CK Mitigations 1

Details

MITRE ATT&CK Detection Strategies
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MITRE ATT&CK Mitigations
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