malcontent

 _ _    _.  .    _   _    _  .  ___   _.   _  .  ___
( | )  (_|  |_  (_  (_)  ( \_)   |   (/_  ( \_)   |

            subtle malware discovery tool

malcontent discovers supply-chain compromises through the magic of context, differential analysis, and 14,000+ YARA rules.

 ________      ________      ________      ________
|        |    |        |    |        |    |        |
| v1.0.0 | => | v1.0.1 | => | v1.0.2 | => | v1.0.3 |
|________|    |________|    |________|    |________|

               unchanged     HIGH-RISK     decreased
               risk          increase      risk

malcontent has 3 modes of operation:

• ✨ diff: risk-weighted differential analysis between two programs
• 🕵️‍♀️ analyze: deep analysis of a program's capabilities
• 🔍 scan: basic scan of malicious content

malcontent is at its best analyzing programs that run on Linux. Still, it also performs admirably for programs designed for other UNIX platforms such as macOS and, to a lesser extent, Windows.

Features

• 14,500+ YARA detection rules
  • Including third-party rules from companies such as Avast, Elastic, FireEye, Mandiant, Nextron, ReversingLabs, and more!
• Analyzes binary files in most common formats (ELF, Mach-O, a.out, PE)
• Analyzes code from most common languages (AppleScript, C, Go, Javascript, PHP, Perl, Ruby, Shell, Typescript)
• Transparent support for archives (apk, tar, zip, etc.) & container images
• Multiple output formats (JSON, YAML, Markdown, Terminal)
• Designed to work as part of a CI/CD pipeline
• Supports air-gapped networks

Modes

Diff

malcontent's most powerful method for discovering malware is through differential analysis against CI/CD artifacts. When used within a build system, malcontent has two significant contextual advantages over a traditional malware scanner:

• Baseline of expected behavior (previous release)
• Semantic versioning that describes how large of a change to expect

Using the 3CX Compromise as an example, malcontent trivially surfaces unexpectedly high-risk changes to libffmpeg:

Each line that begins with a "++" represents a newly added capability. Each capability has a risk score based on how unique it is to malware.

Like the diff(1) command it's based on, malcontent can diff between two binaries or directories. It can also diff two archive files or even two OCI images. Here are some helpful flags:

• --format=markdown: output in markdown for use in GitHub Actions
• --min-file-risk=critical: only show diffs for critical-level changes
• --quantity-increases-risk=false: disable heuristics that increase file criticality due to result frequency
• --file-risk-change: only show diffs for modified files when the source and destination files are of different risks
• --file-risk-increase: only show diffs for modified files when the destination file is of a higher risk than the source file

Scan

malcontent's most basic feature scans directories for possible malware. malcontent is pretty paranoid in this mode, so expect some false positives:

You can also scan a container image: mal scan -i cgr.dev/chainguard/nginx:latest

Useful flags:

• --include-data-files: Include files that do not appear to be programs
• --processes: scan active process binaries (experimental)

Analyze

To enumerate the capabilities of a program, use mal analyze. For example:

The analyze mode emits a list of capabilities often seen in malware, categorized by risk level. It works with programs in a wide variety of file formats and scripting languages.

CRITICAL findings should be considered malicious. Useful flags include:

• --format=json: output to JSON for data parsing
• --min-risk=high: only show high or critical risk findings

Installation

Container

docker pull cgr.dev/chainguard/malcontent:latest

Local

Requirements:

• yara - the rule language
• go - the programming language
• pkg-config - for dependency handling, included in many UNIX distributions

For example, to install the YARA library on Linux or macOS:

brew install yara || sudo apt install libyara-dev \
 || sudo dnf install yara-devel || sudo pacman -S yara

Install malcontent:

go install github.com/chainguard-dev/malcontent/cmd/mal@latest

Help Wanted

malcontent is open source! If you are interested in contributing, check out our development guide. Send us a pull request, and we'll help you with the rest!