IOC defanging modifies potentially malicious indicators (URLs, IP addresses, domains, email addresses) to prevent accidental clicks or execution while preserving readability for analysis and sharing. This skill covers building an automated pipeline that ingests raw IOCs from multiple sources, normalizes and deduplicates them, applies defanging for safe human consumption, converts them to STIX 2.1 format for machine consumption, and distributes through TAXII servers, MISP instances, and email reports.
defang, ioc-fanger, stix2, requests, validators librariesDefanging replaces active protocol and domain components to prevent execution: http:// becomes hxxp://, https:// becomes hxxps://, dots in domains/IPs become [.], @ in emails becomes [@]. This is critical for sharing IOCs in reports, emails, Slack channels, and paste sites where auto-linking could trigger network connections to malicious infrastructure.
Raw IOCs from different sources come in inconsistent formats. Normalization involves converting to lowercase, removing trailing slashes and whitespace, extracting domains from URLs, resolving URL encoding, validating format correctness, and deduplicating across sources.
STIX patterns express IOCs in a standardized format: [ipv4-addr:value = '203.0.113.1'], [domain-name:value = 'malicious.example.com'], [url:value = 'http://evil.com/payload'], [file:hashes.'SHA-256' = 'abc123...']. Each indicator includes valid_from, indicator_types, confidence, and optional TLP markings.
import re
import hashlib
from urllib.parse import urlparse, unquote
from datetime import datetime
class IOCExtractor:
"""Extract and normalize IOCs from text."""
PATTERNS = {
"ipv4": r'\b(?:(?:25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)\.){3}(?:25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)\b',
"domain": r'\b(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,}\b',
"url": r'https?://[^\s<>"{}|\\^`\[\]]+',
"email": r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b',
"md5": r'\b[a-fA-F0-9]{32}\b',
"sha1": r'\b[a-fA-F0-9]{40}\b',
"sha256": r'\b[a-fA-F0-9]{64}\b',
}
WHITELIST_DOMAINS = {
"google.com", "microsoft.com", "amazon.com", "github.com",
"cloudflare.com", "akamai.com", "example.com",
}
def extract_from_text(self, text):
"""Extract all IOC types from free text."""
# Refang any already-defanged indicators first
text = self._refang(text)
iocs = {"ipv4": set(), "domain": set(), "url": set(),
"email": set(), "md5": set(), "sha1": set(), "sha256": set()}
for ioc_type, pattern in self.PATTERNS.items():
matches = re.findall(pattern, text)
for match in matches:
normalized = self._normalize(match, ioc_type)
if normalized and not self._is_whitelisted(normalized, ioc_type):
iocs[ioc_type].add(normalized)
# Remove domains that are part of URLs
url_domains = set()
for url in iocs["url"]:
parsed = urlparse(url)
url_domains.add(parsed.netloc)
iocs["domain"] -= url_domains
total = sum(len(v) for v in iocs.values())
print(f"[+] Extracted {total} unique IOCs from text")
return {k: sorted(v) for k, v in iocs.items()}
def _refang(self, text):
"""Convert defanged indicators back to active form."""
text = text.replace("hxxp://", "http://").replace("hxxps://", "https://")
text = text.replace("[.]", ".").replace("[@]", "@")
text = text.replace("[://]", "://").replace("(.)", ".")
return text
def _normalize(self, value, ioc_type):
"""Normalize an IOC value."""
value = value.strip().lower()
if ioc_type == "url":
value = unquote(value).rstrip("/")
elif ioc_type == "domain":
value = value.rstrip(".")
return value
def _is_whitelisted(self, value, ioc_type):
"""Check if IOC is in whitelist."""
if ioc_type == "domain":
return value in self.WHITELIST_DOMAINS
if ioc_type == "url":
parsed = urlparse(value)
return parsed.netloc in self.WHITELIST_DOMAINS
return False
extractor = IOCExtractor()
sample_text = """
Malware C2: hxxps://evil-domain[.]com/beacon
Drops payload from 192.168.1.100 and contacts 10[.]0[.]0[.]1
SHA256: 275a021bbfb6489e54d471899f7db9d1663fc695ec2fe2a2c4538aabf651fd0f
Phishing email from attacker[@]phishing-domain[.]com
"""
iocs = extractor.extract_from_text(sample_text)
class IOCDefanger:
"""Defang IOCs for safe sharing in reports and communications."""
def defang_url(self, url):
return url.replace("http://", "hxxp://").replace("https://", "hxxps://").replace(".", "[.]")
def defang_domain(self, domain):
return domain.replace(".", "[.]")
def defang_ip(self, ip):
return ip.replace(".", "[.]")
def defang_email(self, email):
return email.replace("@", "[@]").replace(".", "[.]")
def defang_all(self, iocs):
"""Defang all IOCs in a dictionary."""
defanged = {}
for ioc_type, values in iocs.items():
if ioc_type == "url":
defanged[ioc_type] = [self.defang_url(v) for v in values]
elif ioc_type == "domain":
defanged[ioc_type] = [self.defang_domain(v) for v in values]
elif ioc_type == "ipv4":
defanged[ioc_type] = [self.defang_ip(v) for v in values]
elif ioc_type == "email":
defanged[ioc_type] = [self.defang_email(v) for v in values]
else:
defanged[ioc_type] = values # Hashes don't need defanging
return defanged
def generate_sharing_report(self, iocs, defanged, report_name="IOC Report"):
"""Generate a human-readable defanged IOC report."""
report = f"# {report_name}\n"
report += f"Generated: {datetime.now().isoformat()}\n\n"
for ioc_type in ["url", "domain", "ipv4", "email", "sha256", "sha1", "md5"]:
values = defanged.get(ioc_type, [])
if values:
report += f"## {ioc_type.upper()} ({len(values)})\n"
for v in values:
report += f"- `{v}`\n"
report += "\n"
return report
defanger = IOCDefanger()
defanged = defanger.defang_all(iocs)
report = defanger.generate_sharing_report(iocs, defanged, "Malware Campaign IOCs")
print(report)
from stix2 import Indicator, Bundle, TLP_WHITE, TLP_GREEN, TLP_AMBER
from datetime import datetime
class STIXConverter:
"""Convert raw IOCs to STIX 2.1 Indicator objects."""
TLP_MAP = {"white": TLP_WHITE, "green": TLP_GREEN, "amber": TLP_AMBER}
def iocs_to_stix(self, iocs, tlp="green", confidence=75):
"""Convert IOC dictionary to STIX 2.1 bundle."""
stix_objects = []
marking = self.TLP_MAP.get(tlp, TLP_GREEN)
for ip in iocs.get("ipv4", []):
stix_objects.append(Indicator(
name=f"Malicious IP: {ip}",
pattern=f"[ipv4-addr:value = '{ip}']",
pattern_type="stix",
valid_from=datetime.now(),
indicator_types=["malicious-activity"],
confidence=confidence,
object_marking_refs=[marking],
))
for domain in iocs.get("domain", []):
stix_objects.append(Indicator(
name=f"Malicious Domain: {domain}",
pattern=f"[domain-name:value = '{domain}']",
pattern_type="stix",
valid_from=datetime.now(),
indicator_types=["malicious-activity"],
confidence=confidence,
object_marking_refs=[marking],
))
for url in iocs.get("url", []):
escaped = url.replace("'", "\\'")
stix_objects.append(Indicator(
name=f"Malicious URL: {url[:60]}",
pattern=f"[url:value = '{escaped}']",
pattern_type="stix",
valid_from=datetime.now(),
indicator_types=["malicious-activity"],
confidence=confidence,
object_marking_refs=[marking],
))
for sha256 in iocs.get("sha256", []):
stix_objects.append(Indicator(
name=f"Malicious File Hash: {sha256[:16]}...",
pattern=f"[file:hashes.'SHA-256' = '{sha256}']",
pattern_type="stix",
valid_from=datetime.now(),
indicator_types=["malicious-activity"],
confidence=confidence,
object_marking_refs=[marking],
))
bundle = Bundle(objects=stix_objects)
print(f"[+] Created STIX bundle with {len(stix_objects)} indicators")
return bundle
converter = STIXConverter()
stix_bundle = converter.iocs_to_stix(iocs, tlp="amber", confidence=80)
with open("iocs_stix_bundle.json", "w") as f:
f.write(stix_bundle.serialize(pretty=True))
import requests
import json
class IOCDistributor:
"""Distribute IOCs through various channels."""
def push_to_misp(self, iocs, misp_url, misp_key, event_info):
"""Push IOCs to MISP as a new event."""
headers = {
"Authorization": misp_key,
"Content-Type": "application/json",
"Accept": "application/json",
}
event = {
"Event": {
"info": event_info,
"distribution": "1", # This community only
"threat_level_id": "2", # Medium
"analysis": "2", # Completed
"Attribute": [],
}
}
type_mapping = {
"ipv4": "ip-dst",
"domain": "domain",
"url": "url",
"email": "email-src",
"md5": "md5",
"sha1": "sha1",
"sha256": "sha256",
}
for ioc_type, values in iocs.items():
misp_type = type_mapping.get(ioc_type)
if misp_type:
for value in values:
event["Event"]["Attribute"].append({
"type": misp_type,
"value": value,
"category": "Network activity" if ioc_type in ("ipv4", "domain", "url") else "Payload delivery",
"to_ids": True,
})
resp = requests.post(
f"{misp_url}/events",
headers=headers,
json=event,
verify=False,
)
if resp.status_code == 200:
event_id = resp.json().get("Event", {}).get("id", "")
print(f"[+] MISP event created: {event_id}")
return event_id
else:
print(f"[-] MISP error: {resp.status_code} - {resp.text[:200]}")
return None
def push_to_taxii(self, stix_bundle, taxii_url, collection_id, username, password):
"""Push STIX bundle to TAXII 2.1 collection."""
from taxii2client.v21 import Collection
collection = Collection(
f"{taxii_url}/collections/{collection_id}/",
user=username, password=password,
)
response = collection.add_objects(stix_bundle.serialize())
print(f"[+] TAXII: Published bundle, status: {response.status}")
return response
distributor = IOCDistributor()
distributor.push_to_misp(
iocs,
misp_url="https://misp.organization.com",
misp_key="YOUR_MISP_API_KEY",
event_info="Malware Campaign IOCs - 2025",
)