Obfuscated Files or Information: Software Packing

Adversaries may perform software packing or virtual machine software protection to conceal their code. Software packing is a method of compressing or encrypting an executable. Packing an executable changes the file signature in an attempt to avoid signature-based detection. Most decompression techniques decompress the executable code in memory. Virtual machine software protection translates an executable's original code into a special format that only a special virtual machine can run. A virtual machine is then called to run this code.[1]

Utilities used to perform software packing are called packers. Example packers are MPRESS and UPX. A more comprehensive list of known packers is available, [2] but adversaries may create their own packing techniques that do not leave the same artifacts as well-known packers to evade defenses.

ID: T1027.002
Sub-technique of:  T1027
Tactic: Defense Evasion
Platforms: Windows, macOS
Data Sources: Binary file metadata
Defense Bypassed: Anti-virus, Heuristic detection, Signature-based detection
CAPEC ID: CAPEC-570
Contributors: Filip Kafka, ESET
Version: 1.0
Created: 05 February 2020
Last Modified: 05 February 2020

Procedure Examples

Name Description
Anchor

Anchor has come with a packed payload.[3]

APT29

APT29 used UPX to pack files.[4]

APT3

APT3 has been known to pack their tools.[5]

APT38

APT38 has used several code packing methods such as Themida, Enigma, VMProtect, and Obsidium, to pack their implants.[6]

APT39

APT39 has packed tools with UPX, and has repacked a modified version of Mimikatz to thwart anti-virus detection.[7][8]

Astaroth

Astaroth uses a software packer called Pe123\RPolyCryptor.[9]

China Chopper

China Chopper's client component is packed with UPX.[10]

Dark Caracal

Dark Caracal has used UPX to pack Bandook.[11]

DarkComet

DarkComet has the option to compress its payload using UPX or MPRESS.[12]

Daserf

A version of Daserf uses the MPRESS packer.[13]

Dyre

Dyre has been delivered with encrypted resources and must be unpacked for execution.[14]

Elderwood

Elderwood has packed malware payloads before delivery to victims.[15]

Emotet

Emotet has used custom packers to protect its payloads.[16]

FatDuke

FatDuke has been regularly repacked by its operators to create large binaries and evade detection.[17]

FinFisher

A FinFisher variant uses a custom packer.[18][19]

GreyEnergy

GreyEnergy is packed for obfuscation.[20]

H1N1

H1N1 uses a custom packing algorithm.[21]

HotCroissant

HotCroissant has used the open source UPX executable packer.[22]

IcedID

IcedID has packed and encrypted its loader module.[23]

jRAT

jRAT payloads have been packed.[24]

Lazarus Group

Lazarus Group has used Themida to pack at least two separate backdoor implants.[25]

Lokibot

Lokibot has used several packing methods for obfuscation.[26]

Machete

Machete has been packed with NSIS.[27]

Metamorfo

Metamorfo has used VMProtect to pack and protect files.[28]

Night Dragon

Night Dragon is known to use software packing in its tools.[29]

OopsIE

OopsIE uses the SmartAssembly obfuscator to pack an embedded .Net Framework assembly used for C2.[30]

OSX_OCEANLOTUS.D

OSX_OCEANLOTUS.D has a variant that is packed with UPX.[31]

Patchwork

A Patchwork payload was packed with UPX.[32]

Raindrop

Raindrop used a custom packer for its Cobalt Strike payload, which was compressed using the LZMA algorithm.[33][34]

Rocke

Rocke's miner has created UPX-packed files in the Windows Start Menu Folder.[35][36][37]

SDBot

SDBot has used a packed installer file.[38]

SeaDuke

SeaDuke has been packed with the UPX packer.[39]

ShimRat

ShimRat's loader has been packed with the compressed ShimRat core DLL and the legitimate DLL for it to hijack.[40]

Soft Cell

Soft Cell packed some payloads using different types of packers, both known and custom.[41]

TA505

TA505 has used UPX to obscure malicious code.[38]

The White Company

The White Company has obfuscated their payloads through packing.[42]

TrickBot

TrickBot leverages a custom packer to obfuscate its functionality.[43]

Trojan.Karagany

Trojan.Karagany samples sometimes use common binary packers such as UPX and Aspack on top of a custom Delphi binary packer.[44][45]

Uroburos

Uroburos uses a custom packer.[46]

Valak

Valak has used packed DLL payloads.[47]

VERMIN

VERMIN is initially packed.[48]

yty

yty packs a plugin with UPX.[49]

Zebrocy

Zebrocy's Delphi variant was packed with UPX.[50][51]

ZeroT

Some ZeroT DLL files have been packed with UPX.[52]

Mitigations

Mitigation Description
Antivirus/Antimalware

Employ heuristic-based malware detection. Ensure updated virus definitions and create custom signatures for observed malware.

Detection

Use file scanning to look for known software packers or artifacts of packing techniques. Packing is not a definitive indicator of malicious activity, because legitimate software may use packing techniques to reduce binary size or to protect proprietary code.

References

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