Detect Fileless Storage in Elastic Security
Adversaries may store data in fileless formats to conceal malicious activity from defenses. Fileless storage includes the Windows Registry, event logs, WMI repository, and on Linux, shared memory directories (/dev/shm, /run/shm) and volatile paths (/tmp). Windows Registry-based storage is widely used by malware including QakBot, ComRAT, ShadowPad, DarkWatchman, Turla, APT32, and Volgmer to store encrypted configurations, payloads, and C2 data. Linux malware including FritzFrog (FrogShell), Muhstik, and others abuse /dev/shm and /run/shm to store binaries that are executed directly from shared memory without writing to persistent disk storage.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.011 Fileless Storage
- Canonical reference
- https://attack.mitre.org/techniques/T1027/011/
Elastic Detection Query
registry where
event.action in ("RegistryValueSet", "modification", "creation") and
(
any registry.data.strings : ("*MZ*", "*TVqQ*", "*4D5A*") or
(
length(registry.data.strings[0]) > 5000 and
match(registry.data.strings[0], """^[A-Za-z0-9+/=]{100,}$""")
) or
registry.path : (
"*\\ShellCompatibility*",
"*\\PrintConfigs*",
"*\\Microsoft\\DRM*",
"*\\ApplicationContainer*",
"*\\Plus",
"*\\GameConfiguration*",
"*\\ScConfig*"
)
) and
not registry.path : (
"HKLM\\SYSTEM\\CurrentControlSet\\Services\\*",
"*\\Windows NT\\CurrentVersion\\Winlogon*"
)
/* Companion query for Linux fileless execution — run separately */
/* process where
host.os.type == "linux" and
event.type == "start" and
(
process.command_line : ("*/dev/shm/*", "*/run/shm/*", "*memfd_create*", "*/tmp/.*") or
process.executable : ("/dev/shm/*", "/run/shm/*")
) and
not process.name : ("python", "python3", "java", "node", "nodejs", "ruby", "perl", "Xorg", "dbus-daemon")
*/Detects T1027.011 Fileless Storage via Elastic EQL targeting Windows Registry events with PE magic bytes (MZ, 4D5A, TVqQ) or oversized Base64 blobs in registry value data, and registry key paths associated with malware payload staging (QakBot, Turla, DarkWatchman, ShadowPad, APT32). A commented companion query covers Linux fileless execution from /dev/shm and /run/shm via Elastic Endpoint or Auditbeat process telemetry.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate DRM software (Adobe, Microsoft PlayReady, Widevine) writing large encrypted license blobs to HKLM\SOFTWARE\Microsoft\DRM — will trigger on registry path pattern match
- Enterprise software deployment tools (SCCM client, Chocolatey, Tanium) that temporarily stage Base64-encoded installer payloads in HKCU or HKLM Software subkeys during silent installation workflows
- Linux applications using POSIX shared memory (shm_open) for high-performance IPC — common in PostgreSQL (shared_buffers), multimedia frameworks (PulseAudio), and scientific computing libraries that create files in /dev/shm or execute helpers from those paths
Other platforms for T1027.011
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Store Base64-Encoded Payload in Registry (QakBot/Sibot Pattern)
Expected signal: Sysmon Event ID 12 (Registry Key Creation): new key under HKCU\Software\Microsoft. Sysmon Event ID 13 (Registry Value Set): Config value with Base64 data. PowerShell ScriptBlock Log Event ID 4104: New-ItemProperty command with Base64 value.
- Test 2Store Encrypted Configuration in Non-Standard Registry Path
Expected signal: Sysmon Event ID 12/13: registry key and value creation at HKCU\Software\ApplicationContainer\Appsw64. The Appsw64 key path matches Valak malware's known storage location. Process creation for reg.exe.
- Test 3Execute Binary from Linux Shared Memory (/dev/shm)
Expected signal: Process creation events for cp, chmod, and /dev/shm/fileless_test. Auditd execve records showing execution from /dev/shm path. Process listing would show exe=/dev/shm/fileless_test for the running process.
- Test 4WMI-Based Fileless Storage (Event Subscription)
Expected signal: Sysmon Event ID 19 (WMI Event Filter Activity): new filter created. WMI provider host (WmiPrvSE.exe) activity. The filter is stored in the WMI repository database, not as a file.
References (5)
- https://attack.mitre.org/techniques/T1027/011/
- https://learn.microsoft.com/microsoft-365/security/intelligence/fileless-threats
- https://securelist.com/a-new-secret-stash-for-fileless-malware/106393/
- https://www.elastic.co/guide/en/security/7.17/prebuilt-rule-7-16-3-binary-executed-from-shared-memory-directory.html
- https://www.akamai.com/blog/security-research/fritzfrog-botnet-new-capabilities-log4shell
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