add file attack_nav_mod.py and README.md

src/README.md

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+# Utility Scripts
+
+This folder contains additional resources that may be utilized in conjunction with the [MBC STIX2 repository](/README.md).
+
+| Script | Purpose |
+|:---|:---|
+| attack_nav_mod.py | This script will modify the MBC content by adding `"x_mitre_platforms": ["N/A"]` to all the attack-pattern objects to satisfy the ATT&K Navigator requirements. This field is not provided by MBC because the behaviors defined in the knowledge base do not contain platform specific information. The script will create a new local file that you can copy over to your navigator installation to create MBC layers.  |

src/attack_nav_mod.py

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+import argparse
+import json
+import pathlib
+
+
+def update_content(mbc_path: pathlib.Path) -> None:
+    """
+    This script is meant to locally modify the STIX2 MBC content into
+    something the attack-navigator can support. Since MBC does not give
+    details platforms, the field `x_mitre_platform` is not provided.
+    """
+    with mbc_path.open("r", encoding="utf-8") as f:
+        mbc_objects = json.load(f)
+
+    for mbc_object in mbc_objects["objects"]:
+        if mbc_object["type"] == "attack-pattern":
+            mbc_object["x_mitre_platforms"] = ["N/A"]
+
+    with open("mbc-attack-nav-modified.json", "w", encoding="utf-8") as f:
+        json.dump(mbc_objects, f)
+
+
+def get_argparse() -> argparse.ArgumentParser:
+    """Defines argument parser for this script"""
+    parser = argparse.ArgumentParser(description="Modify MBC content to be compatible with the ATT&CK Navigator")
+    parser.add_argument("--mbc-content-location",
+                        type=lambda path: pathlib.Path(path),
+                        default=pathlib.Path("..", "mbc", "mbc.json"))
+    return parser
+
+
+def main():
+    arg_parser = get_argparse()
+    args = arg_parser.parse_args()
+    update_content(args.mbc_content_location)
+
+
+if __name__ == "__main__":
+    main()