type: attack-pattern
spec_version: 2.1
id: attack-pattern--0d91b3c0-5e50-47c3-949a-2a796f04d144
created: 2024-03-29T12:38:17.135Z
created_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
revoked: no
external_references: source_name: mitre-attack
url: https://attack.mitre.org/techniques/T1027/013
external_id: T1027.013
source_name: File obfuscation
description: Aspen Lindblom, Joseph Goodwin, and Chris Sheldon. (2021, July 19). Shlayer Malvertising Campaigns Still Using Flash Update Disguise. Retrieved March 29, 2024.
url: https://www.crowdstrike.com/blog/shlayer-malvertising-campaigns-still-using-flash-update-disguise/
source_name: SFX - Encrypted/Encoded File
description: Jai Minton. (2023, March 31). How Falcon OverWatch Investigates Malicious Self-Extracting Archives, Decoy Files and Their Hidden Payloads. Retrieved March 29, 2024.
url: https://www.crowdstrike.com/blog/self-extracting-archives-decoy-files-and-their-hidden-payloads/
object_marking_refs: marking-definition--fa42a846-8d90-4e51-bc29-71d5b4802168
modified: 2025-04-15T19:58:05.840Z
name: Encrypted/Encoded File
description: 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](https://attack.mitre.org/techniques/T1027/002), [Steganography](https://attack.mitre.org/techniques/T1027/003), and [Embedded Payloads](https://attack.mitre.org/techniques/T1027/009), 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](https://attack.mitre.org/techniques/T1140)) 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](https://attack.mitre.org/techniques/T1566) 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](https://attack.mitre.org/techniques/T1204)).(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](https://attack.mitre.org/techniques/T1059) execution.
kill_chain_phases: kill_chain_name: mitre-attack
phase_name: defense-evasion
x_mitre_attack_spec_version: 3.2.0
x_mitre_contributors: David Galazin @themalwareman1
Andrew Northern, @ex_raritas
Jai Minton, @Cyberraiju
x_mitre_deprecated: no
x_mitre_domains: enterprise-attack
x_mitre_is_subtechnique: yes
x_mitre_modified_by_ref: identity--c78cb6e5-0c4b-4611-8297-d1b8b55e40b5
x_mitre_platforms: Linux
macOS
Windows
x_mitre_version: 1.1