Collect CSV Custom IOC files

Supported in:

Google secops SIEM

This document explains how to ingest CSV Custom IOC files to Google Security Operations using Google Cloud Storage, it then maps these fields to the UDM, handling various data types like IPs, domains, and hashes, and enriching the output with threat details, entity information, and severity levels.

Before you begin

Ensure that you have the following prerequisites:

A Google SecOps instance
A GCP project with Cloud Storage API enabled
Permissions to create and manage GCS buckets
Permissions to manage IAM policies on GCS buckets
Permissions to create Cloud Run services, Pub/Sub topics, and Cloud Scheduler jobs
Access to one or more CSV IOC feed URLs (HTTPS) or an internal endpoint that serves CSV

Create Google Cloud Storage bucket

Go to the Google Cloud Console.
Select your project or create a new one.
In the navigation menu, go to Cloud Storage > Buckets.
Click Create bucket.

Provide the following configuration details:

Setting	Value
Name your bucket	Enter a globally unique name (for example, `csv-ioc-logs`)
Location type	Choose based on your needs (Region, Dual-region, Multi-region)
Location	Select the location (for example, `us-central1`)
Storage class	Standard (recommended for frequently accessed logs)
Access control	Uniform (recommended)
Protection tools	Optional: Enable object versioning or retention policy

Click Create.

Create service account for Cloud Run function

The Cloud Run function needs a service account with permissions to write to GCS bucket and be invoked by Pub/Sub.

Create service account

In the GCP Console, go to IAM & Admin > Service Accounts.
Click Create Service Account.
Provide the following configuration details:
- Service account name: Enter csv-ioc-collector-sa.
- Service account description: Enter Service account for Cloud Run function to collect CSV IOC files.
Click Create and Continue.
In the Grant this service account access to project section, add the following roles:
1. Click Select a role.
2. Search for and select Storage Object Admin.
3. Click + Add another role.
4. Search for and select Cloud Run Invoker.
5. Click + Add another role.
6. Search for and select Cloud Functions Invoker.
Click Continue.
Click Done.

These roles are required for:

Storage Object Admin: Write logs to GCS bucket
Cloud Run Invoker: Allow Pub/Sub to invoke the function
Cloud Functions Invoker: Allow function invocation

Grant IAM permissions on GCS bucket

Grant the service account write permissions on the GCS bucket:

Go to Cloud Storage > Buckets.
Click your bucket name.
Go to the Permissions tab.
Click Grant access.
Provide the following configuration details:
- Add principals: Enter the service account email (for example, csv-ioc-collector-sa@PROJECT_ID.iam.gserviceaccount.com).
- Assign roles: Select Storage Object Admin.
Click Save.

Create Pub/Sub topic

Create a Pub/Sub topic that Cloud Scheduler will publish to and the Cloud Run function will subscribe to.

In the GCP Console, go to Pub/Sub > Topics.
Click Create topic.
Provide the following configuration details:
- Topic ID: Enter csv-ioc-trigger.
- Leave other settings as default.
Click Create.

Create Cloud Run function to collect CSV IOC files

The Cloud Run function is triggered by Pub/Sub messages from Cloud Scheduler to fetch CSV IOC files from HTTPS endpoints and writes them to GCS.

In the GCP Console, go to Cloud Run.
Click Create service.
Select Function (use an inline editor to create a function).
In the Configure section, provide the following configuration details:

Setting Value

Service name csv-ioc-collector

Region Select region matching your GCS bucket (for example, us-central1)

Runtime Select Python 3.12 or later
In the Trigger (optional) section:
1. Click + Add trigger.
2. Select Cloud Pub/Sub.
3. In Select a Cloud Pub/Sub topic, choose the Pub/Sub topic (csv-ioc-trigger).
4. Click Save.
In the Authentication section:
1. Select Require authentication.
2. Check Identity and Access Management (IAM).
Note: Pub/Sub automatically handles authentication when invoking the function.
Scroll down and expand Containers, Networking, Security.
Go to the Security tab:
- Service account: Select the service account (csv-ioc-collector-sa).

Setting	Value
Service name	`csv-ioc-collector`
Region	Select region matching your GCS bucket (for example, `us-central1`)
Runtime	Select Python 3.12 or later

Go to the Containers tab:

Click Variables & Secrets.
Click + Add variable for each environment variable:

Variable Name	Example Value	Description
`GCS_BUCKET`	`csv-ioc-logs`	GCS bucket name
`GCS_PREFIX`	`csv-ioc`	Prefix for log files
`IOC_URLS`	`https://ioc.example.com/feed.csv,https://another.example.org/iocs.csv`	Comma-separated HTTPS URLs
`AUTH_HEADER`	`Authorization: Bearer <token>`	Optional authentication header
`TIMEOUT`	`60`	Request timeout in seconds

In the Variables & Secrets section, scroll down to Requests:
- Request timeout: Enter 600 seconds (10 minutes).
Go to the Settings tab:
- In the Resources section:
  - Memory: Select 512 MiB or higher.
  - CPU: Select 1.
- Click Done.
In the Revision scaling section:
- Minimum number of instances: Enter 0.
- Maximum number of instances: Enter 100 (or adjust based on expected load).
Click Create.
Wait for the service to be created (1-2 minutes).
After the service is created, the inline code editor opens automatically.

Add function code

Enter main in Function entry point

In the inline code editor, create two files:

First file: main.py:

import functions_framework
from google.cloud import storage
import json
import os
import urllib3
from datetime import datetime, timezone
import time

# Initialize HTTP client with timeouts
http = urllib3.PoolManager(
    timeout=urllib3.Timeout(connect=5.0, read=30.0),
    retries=False,
)

# Initialize Storage client
storage_client = storage.Client()

@functions_framework.cloud_event
def main(cloud_event):
    """
    Cloud Run function triggered by Pub/Sub to fetch CSV IOC feeds over HTTPS and write to GCS.

    Args:
        cloud_event: CloudEvent object containing Pub/Sub message
    """

    # Get environment variables
    bucket_name = os.environ.get('GCS_BUCKET')
    prefix = os.environ.get('GCS_PREFIX', 'csv-ioc').strip('/')
    ioc_urls_str = os.environ.get('IOC_URLS', '')
    auth_header = os.environ.get('AUTH_HEADER', '')
    timeout = int(os.environ.get('TIMEOUT', '60'))

    ioc_urls = [u.strip() for u in ioc_urls_str.split(',') if u.strip()]

    if not bucket_name:
        print('Error: GCS_BUCKET environment variable is required')
        return

    if not ioc_urls:
        print('Error: IOC_URLS must contain at least one HTTPS URL')
        return

    try:
        # Get GCS bucket
        bucket = storage_client.bucket(bucket_name)

        run_ts = int(time.time())
        written = []

        for i, url in enumerate(ioc_urls):
            print(f'Processing URL {i+1}/{len(ioc_urls)}: {url}')

            # Build request
            req_headers = {'Accept': 'text/csv, */*'}

            # Add authentication header if provided
            if auth_header:
                if ':' in auth_header:
                    k, v = auth_header.split(':', 1)
                    req_headers[k.strip()] = v.strip()
                else:
                    req_headers['Authorization'] = auth_header.strip()

            # Fetch data with retries
            data = fetch_with_retries(url, req_headers, timeout)

            if data:
                # Write to GCS
                key = generate_blob_name(prefix, url, run_ts, i)
                blob = bucket.blob(key)
                blob.upload_from_string(data, content_type='text/csv')

                written.append({
                    'url': url,
                    'gcs_key': key,
                    'bytes': len(data)
                })

                print(f'Wrote {len(data)} bytes to gs://{bucket_name}/{key}')
            else:
                print(f'Warning: No data retrieved from {url}')

        print(f'Successfully processed {len(written)} URLs')
        print(json.dumps({'ok': True, 'written': written}, indent=2))

    except Exception as e:
        print(f'Error processing CSV IOC feeds: {str(e)}')
        raise

def fetch_with_retries(url, headers, timeout, max_retries=5):
    """Fetch data from URL with retry logic for 429/5xx errors."""
    if not url.lower().startswith('https://'):
        raise ValueError('Only HTTPS URLs are allowed in IOC_URLS')

    attempt = 0
    backoff = 1.0

    while attempt < max_retries:
        try:
            response = http.request('GET', url, headers=headers, timeout=timeout)

            if response.status == 200:
                return response.data.decode('utf-8')
            elif response.status == 429 or (500 <= response.status < 600):
                print(f'Received status {response.status}, retrying in {backoff}s (attempt {attempt+1}/{max_retries})')
                time.sleep(backoff)
                attempt += 1
                backoff *= 2
            else:
                print(f'Error: Received unexpected status {response.status} from {url}')
                return None

        except Exception as e:
            if attempt < max_retries - 1:
                print(f'Request failed: {str(e)}, retrying in {backoff}s (attempt {attempt+1}/{max_retries})')
                time.sleep(backoff)
                attempt += 1
                backoff *= 2
            else:
                raise

    print(f'Max retries exceeded for {url}')
    return None

def generate_blob_name(prefix, url, run_ts, idx):
    """Generate a unique blob name for the CSV file."""
    # Create a short, filesystem-safe token for the URL
    safe_url = url.replace('://', '_').replace('/', '_').replace('?', '_').replace('&', '_')[:100]

    # Generate timestamp-based path
    timestamp_path = time.strftime('%Y/%m/%d/%H%M%S', time.gmtime(run_ts))

    return f"{prefix}/{timestamp_path}-url{idx:03d}-{safe_url}.csv"

Second file: requirements.txt:

functions-framework==3.*
google-cloud-storage==2.*
urllib3>=2.0.0

Click Deploy to save and deploy the function.
Wait for deployment to complete (2-3 minutes).

Note: The Pub/Sub trigger configuration automatically creates the necessary subscriptions and permissions.

Create Cloud Scheduler job

Cloud Scheduler will publish messages to the Pub/Sub topic at regular intervals, triggering the Cloud Run function.

In the GCP Console, go to Cloud Scheduler.
Click Create Job.

Provide the following configuration details:

Setting	Value
Name	`csv-ioc-collector-hourly`
Region	Select same region as Cloud Run function
Frequency	`0 * * * *` (every hour, on the hour)
Timezone	Select timezone (UTC recommended)
Target type	Pub/Sub
Topic	Select the Pub/Sub topic (`csv-ioc-trigger`)
Message body	`{}` (empty JSON object)

Click Create.

Schedule frequency options

Choose frequency based on log volume and latency requirements:

Frequency	Cron Expression	Use Case
Every 5 minutes	`/5 * * *`	High-volume, low-latency
Every 15 minutes	`/15 * * *`	Medium volume
Every hour	`0 * * * *`	Standard (recommended)
Every 6 hours	`0 /6 * *`	Low volume, batch processing
Daily	`0 0 * * *`	Historical data collection

Test the integration

In the Cloud Scheduler console, find your job (csv-ioc-collector-hourly).
Click Force run to trigger the job manually.
Wait a few seconds.
Go to Cloud Run > Services.
Click on your function name (csv-ioc-collector).
Click the Logs tab.

Verify the function executed successfully. Look for the following:

Processing URL 1/X: https://...
Wrote X bytes to gs://csv-ioc-logs/csv-ioc/YYYY/MM/DD/HHMMSS-url000-...csv
Successfully processed X URLs

Go to Cloud Storage > Buckets.
Click your bucket name (csv-ioc-logs).
Navigate to the prefix folder (csv-ioc/).
Verify that new .csv files were created with the current timestamp.

If you see errors in the logs:

HTTP 401/403: Check AUTH_HEADER environment variable
HTTP 429: Rate limiting - function will automatically retry with backoff
Missing environment variables: Check all required variables are set
Only HTTPS URLs are allowed: Verify IOC_URLS contains only HTTPS URLs

Retrieve the Google SecOps service account

Google SecOps uses a unique service account to read data from your GCS bucket. You must grant this service account access to your bucket.

Get the service account email

Go to SIEM Settings > Feeds.
Click Add New Feed.
Click Configure a single feed.
In the Feed name field, enter a name for the feed (for example, CSV Custom IOC).
Select Google Cloud Storage V2 as the Source type.
Select CSV Custom IOC as the Log type.
Click Get Service Account. A unique service account email is displayed, for example:
```
chronicle-12345678@chronicle-gcp-prod.iam.gserviceaccount.com
```
Copy this email address for use in the next step.

Note: Each Google SecOps instance has a unique service account. Don't use service accounts from other documentation or examples.

Grant IAM permissions to the Google SecOps service account

The Google SecOps service account needs Storage Object Viewer role on your GCS bucket.

Go to Cloud Storage > Buckets.
Click your bucket name (csv-ioc-logs).
Go to the Permissions tab.
Click Grant access.
Provide the following configuration details:
- Add principals: Paste the Google SecOps service account email.
- Assign roles: Select Storage Object Viewer.
Click Save.

Note: If you plan to use the deletion option "Delete transferred files" or "Delete transferred files and empty directories," grant Storage Object Admin role instead of Storage Object Viewer.

Configure a feed in Google SecOps to ingest CSV Custom IOC files

Go to SIEM Settings > Feeds.
Click Add New Feed.
Click Configure a single feed.
In the Feed name field, enter a name for the feed (for example, CSV Custom IOC).
Select Google Cloud Storage V2 as the Source type.
Select CSV Custom IOC as the Log type.
Click Next.
Specify values for the following input parameters:
- Storage bucket URL: Enter the GCS bucket URI with the prefix path:
```
gs://csv-ioc-logs/csv-ioc/
```
  - Replace:
    - csv-ioc-logs: Your GCS bucket name.
    - csv-ioc: Optional prefix/folder path where logs are stored.
  - Examples:
    - Root bucket: gs://csv-ioc-logs/
    - With prefix: gs://csv-ioc-logs/csv-ioc/
    - With subfolder: gs://csv-ioc-logs/ioc-feeds/
  Note: Always include the trailing slash (/) at the end of the URI.
- Source deletion option: Select the deletion option according to your preference:
  - Never: Never deletes any files after transfers (recommended for testing).
  - Delete transferred files: Deletes files after successful transfer.
  - Delete transferred files and empty directories: Deletes files and empty directories after successful transfer.
    
    Note: If you select a deletion option, the service account must have Storage Object Admin role instead of Storage Object Viewer. Update IAM permissions accordingly.
- Maximum File Age: Include files modified in the last number of days. Default is 180 days.
- Asset namespace: The asset namespace.
- Ingestion labels: The label to be applied to the events from this feed.
Click Next.
Review your new feed configuration in the Finalize screen, and then click Submit.

UDM mapping table

Log Field	UDM Mapping	Logic
asn	entity.metadata.threat.detection_fields.asn_label.value	Directly mapped from the "asn" field.
category	entity.metadata.threat.category_details	Directly mapped from the "category" field.
classification	entity.metadata.threat.category_details	Appended to "classification - " and mapped to the "entity.metadata.threat.category_details" field.
column2	entity.entity.hostname	Mapped to "entity.entity.hostname" if [category] matches ". ?ip" or ". ?proxy" and [not_ip] is true.
column2	entity.entity.ip	Merged into "entity.entity.ip" if [category] matches ". ?ip" or ". ?proxy" and [not_ip] is false.
confidence	entity.metadata.threat.confidence_score	Converted to float and mapped to the "entity.metadata.threat.confidence_score" field.
country	entity.entity.location.country_or_region	Directly mapped from the "country" field.
date_first	entity.metadata.threat.first_discovered_time	Parsed as ISO8601 and mapped to the "entity.metadata.threat.first_discovered_time" field.
date_last	entity.metadata.threat.last_updated_time	Parsed as ISO8601 and mapped to the "entity.metadata.threat.last_updated_time" field.
detail	entity.metadata.threat.summary	Directly mapped from the "detail" field.
detail2	entity.metadata.threat.description	Directly mapped from the "detail2" field.
domain	entity.entity.hostname	Directly mapped from the "domain" field.
email	entity.entity.user.email_addresses	Merged into the "entity.entity.user.email_addresses" field.
id	entity.metadata.product_entity_id	Appended to "id - " and mapped to the "entity.metadata.product_entity_id" field.
import_session_id	entity.metadata.threat.detection_fields.import_session_id_label.value	Directly mapped from the "import_session_id" field.
itype	entity.metadata.threat.detection_fields.itype_label.value	Directly mapped from the "itype" field.
lat	entity.entity.location.region_latitude	Converted to float and mapped to the "entity.entity.location.region_latitude" field.
lon	entity.entity.location.region_longitude	Converted to float and mapped to the "entity.entity.location.region_longitude" field.
maltype	entity.metadata.threat.detection_fields.maltype_label.value	Directly mapped from the "maltype" field.
md5	entity.entity.file.md5	Directly mapped from the "md5" field.
media	entity.metadata.threat.detection_fields.media_label.value	Directly mapped from the "media" field.
media_type	entity.metadata.threat.detection_fields.media_type_label.value	Directly mapped from the "media_type" field.
org	entity.metadata.threat.detection_fields.org_label.value	Directly mapped from the "org" field.
resource_uri	entity.entity.url	Mapped to "entity.entity.url" if [itype] does not match "(ip
resource_uri	entity.metadata.threat.url_back_to_product	Mapped to "entity.metadata.threat.url_back_to_product" if [itype] matches "(ip
score	entity.metadata.threat.confidence_details	Directly mapped from the "score" field.
severity	entity.metadata.threat.severity	Converted to uppercase and mapped to the "entity.metadata.threat.severity" field if it matches "LOW", "MEDIUM", "HIGH", or "CRITICAL".
source	entity.metadata.threat.detection_fields.source_label.value	Directly mapped from the "source" field.
source_feed_id	entity.metadata.threat.detection_fields.source_feed_id_label.value	Directly mapped from the "source_feed_id" field.
srcip	entity.entity.ip	Merged into "entity.entity.ip" if [srcip] is not empty and not equal to [value].
state	entity.metadata.threat.detection_fields.state_label.value	Directly mapped from the "state" field.
trusted_circle_ids	entity.metadata.threat.detection_fields.trusted_circle_ids_label.value	Directly mapped from the "trusted_circle_ids" field.
update_id	entity.metadata.threat.detection_fields.update_id_label.value	Directly mapped from the "update_id" field.
value	entity.entity.file.full_path	Mapped to "entity.entity.file.full_path" if [category] matches ".*?file".
value	entity.entity.file.md5	Mapped to "entity.entity.file.md5" if [category] matches ".*?md5" and [value] is a 32-character hexadecimal string.
value	entity.entity.file.sha1	Mapped to "entity.entity.file.sha1" if ([category] matches ". ?md5" and [value] is a 40-character hexadecimal string) or ([category] matches ". ?sha1" and [value] is a 40-character hexadecimal string).
value	entity.entity.file.sha256	Mapped to "entity.entity.file.sha256" if ([category] matches ". ?md5" and [value] is a hexadecimal string and [file_type] is not "md5") or ([category] matches ". ?sha256" and [value] is a hexadecimal string).
value	entity.entity.hostname	Mapped to "entity.entity.hostname" if ([category] matches ". ?domain") or ([category] matches ". ?ip" or ".*?proxy" and [not_ip] is true).
value	entity.entity.url	Mapped to "entity.entity.url" if ([category] matches ".*?url") or ([category] matches "url" and [resource_uri] is not empty).
N/A	entity.metadata.collected_timestamp	Populated with the event timestamp.
N/A	entity.metadata.interval.end_time	Set to a constant value of 253402300799 seconds.
N/A	entity.metadata.interval.start_time	Populated with the event timestamp.
N/A	entity.metadata.vendor_name	Set to a constant value of "Custom IOC".

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