Strelka is a real-time, container-based file scanning system used for threat hunting, threat detection, and incident response. Originally based on the design established by Lockheed Martin's Laika BOSS and similar projects (see: related projects), Strelka's purpose is to perform file extraction and metadata collection at enterprise scale.

Strelka differs from its sibling projects in a few significant ways:

• Core codebase is Go and Python3.6+
• Server components run in containers for ease and flexibility of deployment
• OS-native client applications for Windows, Mac, and Linux
• Built using libraries and formats that allow cross-platform, cross-language support

Strelka is a modular data scanning platform, allowing users or systems to submit files for the purpose of analyzing, extracting, and reporting file content and metadata. Coupled with a SIEM, Strelka is able to aggregate, alert, and provide analysts with the capability to better understand their environment without having to perform direct data gathering or time-consuming file analysis.

Running a file through Strelka is simple. In this section, Strelka capabilities of extraction and analysis are demonstrated for a one-off analysis.

Please review the documentation for details on how to properly build and deploy Strelka in an enterprise environment.

# Ubuntu 22.04
sudo apt install -y wget git docker docker-compose jq

git clone https://github.com/target/strelka.git
cd strelka

git clone https://github.com/Yara-Rules/rules.git configs/python/backend/yara
echo 'include "./rules/index.yar"' > configs/python/backend/yara/rules.yara

docker-compose -f build/docker-compose.yaml build
docker-compose -f build/docker-compose.yaml up -d

Use any malware sample, or other file you'd like Strelka to analyze.

wget https://github.com/ytisf/theZoo/raw/master/malware/Binaries/Win32.Emotet/Win32.Emotet.zip -P samples/

docker-compose -f build/docker-compose.yaml run oneshot -f /samples/Win32.Emotet.zip | jq

1. Strelka determined that the submitted file was an encrypted ZIP using the taste configuration
   • configs/python/backend/taste/taste.yara
   • configs/python/backend/backend.yaml
2. Strelka ran the ScanEncryptedZip scanner (and a few others), based on the file type
3. ScanEncryptedZip used a dictionary to crack the ZIP file password, and extract the compressed file
4. The extracted file was sent back into the Strelka pipeline for analysis (note the file.depth field)
5. Strelka determined that the extracted file was an EXE
6. Strelka ran the ScanPe scanner (and a few others), based on the file type
7. ScanPe dissected the EXE file and added useful metadata to the output
8. ScanYara analyzed the EXE file using the provided rules and added numerous matches to the output, some indicating the file might be malicious

The following output has been edited for brevity.

{
  "file": {
    "depth": 0,
    "flavors": {
      "mime": ["application/zip"],
      "yara": ["encrypted_zip", "zip_file"]
    },
    "scanners": [
      "ScanEncryptedZip",
      "ScanEntropy",
      "ScanFooter",
      "ScanHash",
      "ScanHeader",
      "ScanYara",
      "ScanZip"
    ]
  },
  "scan": {
    "encrypted_zip": {
      "cracked_password": "infected",
      "elapsed": 0.114269,
      "total": {"extracted": 1, "files": 1}
    }
  }
}

{
  "file": {
    "depth": 1,
    "flavors": {
      "mime": ["application/x-dosexec"],
      "yara": ["mz_file"]
    },
    "name": "29D6161522C7F7F21B35401907C702BDDB05ED47.bin",
    "scanners": [
      "ScanEntropy",
      "ScanFooter",
      "ScanHash",
      "ScanHeader",
      "ScanPe",
      "ScanYara"
    ]
  },
  "scan": {
    "pe": {
      "address_of_entry_point": 5168,
      "base_of_code": 4096,
      "base_of_data": 32768,
      "checksum": 47465,
      "compile_time": "2015-03-31T08:53:51",
      "elapsed": 0.013076,
      "file_alignment": 4096,
      "file_info": {
        "company_name": "In CSS3",
        "file_description": "Note: In CSS3, the text-decoration property is a shorthand property for text-decoration-line, text-decoration-color, and text-decoration-style, but this is currently.",
        "file_version": "1.00.0065",
        "fixed": {"operating_systems": ["WINDOWS32"]},
        "internal_name": "Callstb",
        "original_filename": "NOFAstb.exe",
        "product_name": "Goodreads",
        "product_version": "1.00.0065",
        "var": {"character_set": "Unicode", "language": "U.S. English"}
      }
    },
    "yara": {
      "elapsed": 0.068918,
      "matches": [
        "SEH__vba",
        "SEH_Init",
        "Big_Numbers1",
        "IsPE32",
        "IsWindowsGUI",
        "HasOverlay",
        "HasRichSignature",
        "Microsoft_Visual_Basic_v50v60",
        "Microsoft_Visual_Basic_v50",
        "Microsoft_Visual_Basic_v50_v60",
        "Microsoft_Visual_Basic_v50_additional",
        "Microsoft_Visual_Basic_v50v60_additional"
      ],
      "tags": [
        "AntiDebug",
        "SEH",
        "Tactic_DefensiveEvasion",
        "Technique_AntiDebugging",
        "SubTechnique_SEH",
        "PECheck",
        "PEiD"
      ]
    }
  }
}

If Strelka was deployed and ingesting files in your environment, you might be collecting these events in your SIEM. With this analysis, you could write a rule that looks for events matching the suspicious yara tags, alerting you to a potentially malicious file.

scan.yara.tags:("Technique_AntiDebugging" && "SubTechnique_SEH")

With over 50 file scanners for the most common file types (e.g., exe, docx, js, zip), Strelka provides users with the ability to gain new insights into files on their host, network, or enterprise. While Strelka is not a detection engine itself (although it does utilize YARA, it can provide enough metadata to identify suspicious or malicious files. Some potential uses for Strelka include:

More documentation about Strelka can be found in the README, including:

• Installation
• Deployment
• Design
• Architecture
• FAQ

Guidelines for contributing can be found here.

See issues labeled bug in the tracker for any potential known issues.

• Laika BOSS
• File Scanning Framework
• Assemblyline

Strelka and its associated code is released under the terms of the Apache 2.0 License.