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Encrypted/Encoded File (T1027.013) is a MITRE ATT&CK technique associated with Stealth . Adversaries may encrypt or encode files to obfuscate strings, bytes, and other specific patterns to impede detection.
Encrypted/Encoded File (T1027.013) is a MITRE ATT&CK technique associated with Stealth. Adversaries may encrypt or encode files to obfuscate strings, bytes, and other specific patterns to impede detection.
Attackers use Encrypted/Encoded File because it provides a reliable way to advance their objective within the Stealth tactic, often with a favorable balance of impact versus detectability on Linux, macOS, Windows environments. Defenders should assess this behavior in the context of the affected platform and adjacent activity rather than treating it as a standalone indicator.
Adversaries may encrypt or encode files to obfuscate strings, bytes, and other specific patterns to impede detection. Encrypting and/or encoding file content aims to conceal malicious artifacts within a file used in an intrusion. Many other techniques, such as Software Packing, Steganography, and Embedded Payloads, share this same broad objective. Encrypting and/or encoding files could lead to a lapse in detection of static signatures, only for this malicious content to be revealed (i.e., Deobfuscate/Decode Files or Information) at the time of execution/use.
This type of file obfuscation can be applied to many file artifacts present on victim hosts, such as malware log/configuration and payload files.(Citation: File obfuscation) Files can be encrypted with a hardcoded or user-supplied key, as well as otherwise obfuscated using standard encoding schemes such as Base64.
The entire content of a file may be obfuscated, or just specific functions or values (such as C2 addresses). Encryption and encoding may also be applied in redundant layers for additional protection.
For example, adversaries may abuse password-protected Word documents or self-extracting (SFX) archives as a method of encrypting/encoding a file such as a Phishing payload. These files typically function by attaching the intended archived content to a decompressor stub that is executed when the file is invoked (e.g., User Execution).(Citation: SFX - Encrypted/Encoded File)
Adversaries may also abuse file-specific as well as custom encoding schemes. For example, Byte Order Mark (BOM) headers in text files may be abused to manipulate and obfuscate file content until Command and Scripting Interpreter execution.
No universal command represents Encrypted/Encoded File. Capture the exact command line, arguments, parent process, account, host, and execution time from the investigated environment; do not operationalize unverified examples.
| Event ID | Log Channel | What It Indicates |
|---|---|---|
| Environment-specific | Relevant Windows channel(s) | Correlate authentication, process, object-access, and configuration events with the observed execution context. |
| Sysmon Event ID | Name | Why It's Relevant Here |
|---|---|---|
| Environment-specific | Validate configured telemetry | Use process, network, file, registry, DNS, or image-load telemetry only when relevant and enabled. |
No MITRE detection guidance published for this technique.
Relevant ATT&CK Data Sources: N/A
A universal Sigma rule would create unreliable results because this technique has no single guaranteed observable. Build detection logic from a documented behavior and supported data source, scope it to the affected platform, and validate it against benign administrative activity before deployment.
Start with the data sources named in the detection section. Scope searches by asset, identity, and time window; correlate the primary behavior with preceding access and subsequent actions. A portable query is intentionally not provided where the technique lacks a universal schema or observable.