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MITRE ATT&CK · T1027

Obfuscated Files or Information

MITRE · cited in 27 of our lessons

Explanation

What attackers do. Attackers encrypt, encode, pack or otherwise disguise files, scripts and commands so that security tools and analysts cannot easily read them. This serves the Defence Evasion tactic and appears in almost every stage of an intrusion.

How to defend. Use security tools that analyse behaviour at run time rather than only static signatures, and enable script logging that records content after it is decoded, such as PowerShell script block logging and AMSI integration. Sandbox suspicious files and archives. Application control limits the impact even when a payload is not recognised.

Signs to look for. Look for long Base64 strings in command lines, high entropy files, password-protected archives in email, scripts built from many concatenated fragments, and packed executables with few readable strings. A common gap is inspecting only the outer layer of nested archives or encoded scripts.

Open the technique on MITRE ATT&CK
The official text
Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit. This is common behavior that can be used across different platforms and the network to evade defenses. Payloads may be compressed, archived, or encrypted in order to avoid detection. These payloads may be used during Initial Access or later to mitigate detection. Sometimes a user's action may be required to open and Deobfuscate/Decode Files or Information for User Execution. The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary. Adversaries may also use compressed or archived scripts, such as JavaScript. Portions of files can also be encoded to hide the plain-text strings that would otherwise help defenders with discovery. Payloads may also be split into separate, seemingly benign files that only reveal malicious functionality when reassembled.

© The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation (MITRE ATT&CK®).

Lessons that cite it

Real incidents where this item mattered: the latest 12 of 27.