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443 lines
16 KiB
Python
443 lines
16 KiB
Python
# Mobile Verification Toolkit (MVT)
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# Copyright (c) 2021 The MVT Project Authors.
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# Use of this software is governed by the MVT License 1.1 that can be found at
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# https://license.mvt.re/1.1/
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import io
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import json
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import os
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import requests
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from appdirs import user_data_dir
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from .url import URL
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class Indicators:
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"""This class is used to parse indicators from a STIX2 file and provide
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functions to compare extracted artifacts to the indicators.
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"""
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def __init__(self, log=None):
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self.data_dir = user_data_dir("mvt")
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self.log = log
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self.ioc_files = []
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self.total_ioc_count = 0
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def _load_downloaded_indicators(self):
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if not os.path.isdir(self.data_dir):
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return
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for f in os.listdir(self.data_dir):
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if f.lower().endswith(".stix2"):
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self.parse_stix2(os.path.join(self.data_dir, f))
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def _check_stix2_env_variable(self):
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"""
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Checks if a variable MVT_STIX2 contains path to STIX Files.
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"""
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if "MVT_STIX2" not in os.environ:
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return
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paths = os.environ["MVT_STIX2"].split(":")
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for path in paths:
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if os.path.isfile(path):
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self.parse_stix2(path)
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else:
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self.log.info("Invalid STIX2 path %s in MVT_STIX2 environment variable", path)
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def _generate_indicators_file(self):
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return {
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"name": "",
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"description": "",
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"file_name": "",
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"file_path": "",
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"domains": [],
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"processes": [],
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"emails": [],
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"file_names": [],
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"file_paths": [],
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"files_sha256": [],
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"app_ids": [],
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"ios_profile_ids": [],
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"count": 0,
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}
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def _add_indicator(self, ioc, ioc_file, iocs_list):
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if ioc not in iocs_list:
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iocs_list.append(ioc)
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ioc_file["count"] += 1
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self.total_ioc_count += 1
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def parse_stix2(self, file_path):
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"""Extract indicators from a STIX2 file.
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:param file_path: Path to the STIX2 file to parse
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:type file_path: str
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"""
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self.log.info("Parsing STIX2 indicators file at path %s", file_path)
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ioc_file = self._generate_indicators_file()
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ioc_file["file_path"] = file_path
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ioc_file["file_name"] = os.path.basename(file_path)
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with open(file_path, "r") as handle:
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try:
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data = json.load(handle)
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except json.decoder.JSONDecodeError:
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self.log.critical("Unable to parse STIX2 indicator file. The file is malformed or in the wrong format.")
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return
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for entry in data.get("objects", []):
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entry_type = entry.get("type", "")
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if entry_type == "malware":
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ioc_file["name"] = entry.get("name", "") or ioc_file["file_name"]
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ioc_file["description"] = entry.get("description", "") or ioc_file["file_name"]
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continue
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if entry_type != "indicator":
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continue
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key, value = entry.get("pattern", "").strip("[]").split("=")
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value = value.strip("'")
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if key == "domain-name:value":
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# We force domain names to lower case.
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self._add_indicator(ioc=value.lower(),
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ioc_file=ioc_file,
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iocs_list=ioc_file["domains"])
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elif key == "process:name":
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self._add_indicator(ioc=value,
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ioc_file=ioc_file,
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iocs_list=ioc_file["processes"])
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elif key == "email-addr:value":
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# We force email addresses to lower case.
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self._add_indicator(ioc=value.lower(),
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ioc_file=ioc_file,
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iocs_list=ioc_file["emails"])
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elif key == "file:name":
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self._add_indicator(ioc=value,
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ioc_file=ioc_file,
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iocs_list=ioc_file["file_names"])
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elif key == "file:path":
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self._add_indicator(ioc=value,
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ioc_file=ioc_file,
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iocs_list=ioc_file["file_paths"])
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elif key == "file:hashes.sha256":
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self._add_indicator(ioc=value,
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ioc_file=ioc_file,
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iocs_list=ioc_file["files_sha256"])
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elif key == "app:id":
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self._add_indicator(ioc=value,
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ioc_file=ioc_file,
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iocs_list=ioc_file["app_ids"])
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elif key == "configuration-profile:id":
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self._add_indicator(ioc=value,
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ioc_file=ioc_file,
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iocs_list=ioc_file["ios_profile_ids"])
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self.log.info("Loaded %d indicators from \"%s\" indicators file",
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ioc_file["count"], ioc_file["name"])
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self.ioc_files.append(ioc_file)
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def load_indicators_files(self, files, load_default=True):
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"""
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Load a list of indicators files.
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"""
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for file_path in files:
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if os.path.isfile(file_path):
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self.parse_stix2(file_path)
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else:
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self.log.warning("This indicators file %s does not exist", file_path)
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# Load downloaded indicators and any indicators from env variable.
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if load_default:
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self._load_downloaded_indicators()
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self._check_stix2_env_variable()
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self.log.info("Loaded a total of %d unique indicators", self.total_ioc_count)
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def get_iocs(self, ioc_type):
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for ioc_file in self.ioc_files:
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for ioc in ioc_file.get(ioc_type, []):
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yield {
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"value": ioc,
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"type": ioc_type,
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"name": ioc_file["name"]
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}
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def check_domain(self, url):
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"""Check if a given URL matches any of the provided domain indicators.
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:param url: URL to match against domain indicators
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:type url: str
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:returns: Indicator details if matched, otherwise None
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"""
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# TODO: If the IOC domain contains a subdomain, it is not currently
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# being matched.
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if not url:
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return None
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try:
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# First we use the provided URL.
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orig_url = URL(url)
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if orig_url.check_if_shortened():
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# If it is, we try to retrieve the actual URL making an
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# HTTP HEAD request.
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unshortened = orig_url.unshorten()
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# self.log.info("Found a shortened URL %s -> %s",
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# url, unshortened)
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# Now we check for any nested URL shorteners.
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dest_url = URL(unshortened)
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if dest_url.check_if_shortened():
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# self.log.info("Original URL %s appears to shorten another shortened URL %s ... checking!",
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# orig_url.url, dest_url.url)
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return self.check_domain(dest_url.url)
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final_url = dest_url
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else:
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# If it's not shortened, we just use the original URL object.
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final_url = orig_url
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except Exception:
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# If URL parsing failed, we just try to do a simple substring
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# match.
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for ioc in self.get_iocs("domains"):
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if ioc["value"].lower() in url:
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self.log.warning("Maybe found a known suspicious domain %s matching indicators from \"%s\"",
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url, ioc["name"])
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return ioc
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# If nothing matched, we can quit here.
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return None
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# If all parsing worked, we start walking through available domain indicators.
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for ioc in self.get_iocs("domains"):
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# First we check the full domain.
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if final_url.domain.lower() == ioc["value"]:
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if orig_url.is_shortened and orig_url.url != final_url.url:
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self.log.warning("Found a known suspicious domain %s shortened as %s matching indicators from \"%s\"",
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final_url.url, orig_url.url, ioc["name"])
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else:
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self.log.warning("Found a known suspicious domain %s matching indicators from \"%s\"",
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final_url.url, ioc["name"])
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return ioc
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# Then we just check the top level domain.
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if final_url.top_level.lower() == ioc["value"]:
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if orig_url.is_shortened and orig_url.url != final_url.url:
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self.log.warning("Found a sub-domain with suspicious top level %s shortened as %s matching indicators from \"%s\"",
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final_url.url, orig_url.url, ioc["name"])
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else:
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self.log.warning("Found a sub-domain with a suspicious top level %s matching indicators from \"%s\"",
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final_url.url, ioc["name"])
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return ioc
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def check_domains(self, urls):
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"""Check a list of URLs against the provided list of domain indicators.
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:param urls: List of URLs to check against domain indicators
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:type urls: list
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:returns: Indicator details if matched, otherwise None
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"""
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if not urls:
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return None
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for url in urls:
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check = self.check_domain(url)
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if check:
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return check
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def check_process(self, process):
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"""Check the provided process name against the list of process
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indicators.
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:param process: Process name to check against process indicators
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:type process: str
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:returns: Indicator details if matched, otherwise None
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"""
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if not process:
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return None
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proc_name = os.path.basename(process)
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for ioc in self.get_iocs("processes"):
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if proc_name == ioc["value"]:
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self.log.warning("Found a known suspicious process name \"%s\" matching indicators from \"%s\"",
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process, ioc["name"])
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return ioc
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if len(proc_name) == 16:
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if ioc["value"].startswith(proc_name):
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self.log.warning("Found a truncated known suspicious process name \"%s\" matching indicators from \"%s\"",
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process, ioc["name"])
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return ioc
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def check_processes(self, processes):
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"""Check the provided list of processes against the list of
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process indicators.
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:param processes: List of processes to check against process indicators
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:type processes: list
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:returns: Indicator details if matched, otherwise None
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"""
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if not processes:
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return None
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for process in processes:
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check = self.check_process(process)
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if check:
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return check
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def check_email(self, email):
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"""Check the provided email against the list of email indicators.
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:param email: Email address to check against email indicators
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:type email: str
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:returns: Indicator details if matched, otherwise None
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"""
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if not email:
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return None
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for ioc in self.get_iocs("emails"):
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if email.lower() == ioc["value"].lower():
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self.log.warning("Found a known suspicious email address \"%s\" matching indicators from \"%s\"",
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email, ioc["name"])
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return ioc
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def check_file_name(self, file_name):
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"""Check the provided file name against the list of file indicators.
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:param file_name: File name to check against file
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indicators
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:type file_name: str
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:returns: Indicator details if matched, otherwise None
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"""
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if not file_name:
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return None
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for ioc in self.get_iocs("file_names"):
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if ioc["value"] == file_name:
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self.log.warning("Found a known suspicious file name \"%s\" matching indicators from \"%s\"",
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file_name, ioc["name"])
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return ioc
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def check_file_path(self, file_path):
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"""Check the provided file path against the list of file indicators (both path and name).
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:param file_path: File path or file name to check against file
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indicators
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:type file_path: str
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:returns: Indicator details if matched, otherwise None
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"""
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if not file_path:
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return None
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ioc = self.check_file_name(os.path.basename(file_path))
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if ioc:
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return ioc
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for ioc in self.get_iocs("file_paths"):
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# Strip any trailing slash from indicator paths to match directories.
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if file_path.startswith(ioc["value"].rstrip("/")):
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self.log.warning("Found a known suspicious file path \"%s\" matching indicators form \"%s\"",
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file_path, ioc["name"])
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return ioc
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def check_profile(self, profile_uuid):
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"""Check the provided configuration profile UUID against the list of indicators.
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:param profile_uuid: Profile UUID to check against configuration profile indicators
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:type profile_uuid: str
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:returns: Indicator details if matched, otherwise None
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"""
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if not profile_uuid:
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return None
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for ioc in self.get_iocs("ios_profile_ids"):
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if profile_uuid in ioc["value"]:
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self.log.warning("Found a known suspicious profile ID \"%s\" matching indicators from \"%s\"",
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profile_uuid, ioc["name"])
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return ioc
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def check_file_hash(self, file_hash):
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"""Check the provided SHA256 file hash against the list of indicators.
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:param file_hash: SHA256 hash to check
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:type file_hash: str
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:returns: Indicator details if matched, otherwise None
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"""
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if not file_hash:
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return None
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for ioc in self.get_iocs("files_sha256"):
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if file_hash.lower() == ioc["value"].lower():
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self.log.warning("Found a known suspicious file with hash \"%s\" matching indicators from \"%s\"",
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file_hash, ioc["name"])
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return ioc
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def check_app_id(self, app_id):
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"""Check the provided app identifier (typically an Android package name)
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against the list of indicators.
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:param app_id: App ID to check against the list of indicators
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:type app_id: str
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:returns: Indicator details if matched, otherwise None
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"""
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if not app_id:
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return None
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for ioc in self.get_iocs("app_ids"):
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if app_id.lower() == ioc["value"].lower():
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self.log.warning("Found a known suspicious app with ID \"%s\" matching indicators from \"%s\"",
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app_id, ioc["name"])
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return ioc
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def download_indicators_files(log):
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"""
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Download indicators from repo into MVT app data directory.
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"""
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data_dir = user_data_dir("mvt")
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if not os.path.isdir(data_dir):
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os.makedirs(data_dir, exist_ok=True)
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# Download latest list of indicators from the MVT repo.
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res = requests.get("https://github.com/mvt-project/mvt/raw/main/public_indicators.json")
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if res.status_code != 200:
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log.warning("Unable to find retrieve list of indicators from the MVT repository.")
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return
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for ioc_entry in res.json():
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ioc_url = ioc_entry["stix2_url"]
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log.info("Downloading indicator file '%s' from '%s'", ioc_entry["name"], ioc_url)
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res = requests.get(ioc_url)
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if res.status_code != 200:
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log.warning("Could not find indicator file '%s'", ioc_url)
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continue
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clean_file_name = ioc_url.lstrip("https://").replace("/", "_")
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ioc_path = os.path.join(data_dir, clean_file_name)
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# Write file to disk. This will overwrite any older version of the STIX2 file.
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with io.open(ioc_path, "w") as f:
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f.write(res.text)
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log.info("Saved indicator file to '%s'", os.path.basename(ioc_path))
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