Collect CSV Custom IOC files

This document explains how to ingest CSV Custom IOC files to Google Security Operations using Amazon S3. 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

• Google SecOps instance
• Privileged access to AWS (S3, IAM, Lambda, EventBridge)
• Access to one or more CSV IOC feed URLs (HTTPS) or an internal endpoint that serves CSV

Configure AWS S3 bucket and IAM for Google SecOps

1. Create Amazon S3 bucket following this user guide: Creating a bucket
2. Save bucket Name and Region for future reference (for example, csv-ioc).
3. Create a user following this user guide: Creating an IAM user.
4. Select the created User.
5. Select the Security credentials tab.
6. Click Create Access Key in the Access Keys section.
7. Select Third-party service as the Use case.
8. Click Next.
9. Optional: add a description tag.
10. Click Create access key.
11. Click Download CSV file to save the Access Key and Secret Access Key for later use.
12. Click Done.
13. Select the Permissions tab.
14. Click Add permissions in the Permissions policies section.
15. Select Add permissions.
16. Select Attach policies directly
17. Search for and select the AmazonS3FullAccess policy.
18. Click Next.
19. Click Add permissions.

Configure the IAM policy and role for S3 uploads

1. Go to AWS console > IAM > Policies > Create policy > JSON tab.

2. Enter the following policy:

   {
     "Version": "2012-10-17",
     "Statement": [
       {
         "Sid": "AllowPutCsvIocObjects",
         "Effect": "Allow",
         "Action": "s3:PutObject",
         "Resource": "arn:aws:s3:::csv-ioc/*"
       }
     ]
   }
   

   • Replace csv-ioc if you entered a different bucket name.

3. Click Next > Create policy.

4. Go to IAM > Roles > Create role > AWS service > Lambda.

5. Attach the newly created policy.

6. Name the role WriteCsvIocToS3Role and click Create role.

Create the Lambda function

1. In the AWS Console, go to Lambda > Functions > Create function.
2. Click Author from scratch.

3. Provide the following configuration details:

   Setting	Value
   Name	csv_custom_ioc_to_s3
   Runtime	Python 3.13
   Architecture	x86_64
   Execution role	WriteCsvIocToS3Role

4. After the function is created, open the Code tab, delete the stub and enter the following code (csv_custom_ioc_to_s3.py):

   #!/usr/bin/env python3
   # Lambda: Pull CSV IOC feeds over HTTPS and write raw CSV to S3 (no transform)
   # - Multiple URLs (comma-separated)
   # - Optional auth header
   # - Retries for 429/5xx
   # - Unique filenames per page
   # - Sets ContentType=text/csv
   
   import os, time, json
   from urllib.request import Request, urlopen
   from urllib.error import HTTPError, URLError
   import boto3
   
   BUCKET = os.environ["S3_BUCKET"]
   PREFIX = os.environ.get("S3_PREFIX", "csv-ioc/").strip("/")
   IOC_URLS = [u.strip() for u in os.environ.get("IOC_URLS", "").split(",") if u.strip()]
   AUTH_HEADER = os.environ.get("AUTH_HEADER", "")  # e.g., "Authorization: Bearer <token>" OR just "Bearer <token>"
   TIMEOUT = int(os.environ.get("TIMEOUT", "60"))
   
   s3 = boto3.client("s3")
   
   def _build_request(url: str) -> Request:
       if not url.lower().startswith("https://"):
           raise ValueError("Only HTTPS URLs are allowed in IOC_URLS")
       req = Request(url, method="GET")
       # Auth header: either "Header-Name: value" or just "Bearer token" -> becomes Authorization
       if AUTH_HEADER:
           if ":" in AUTH_HEADER:
               k, v = AUTH_HEADER.split(":", 1)
               req.add_header(k.strip(), v.strip())
           else:
               req.add_header("Authorization", AUTH_HEADER.strip())
       req.add_header("Accept", "text/csv, */*")
       return req
   
   def _http_bytes(req: Request, timeout: int = TIMEOUT, max_retries: int = 5) -> bytes:
       attempt, backoff = 0, 1.0
       while True:
           try:
               with urlopen(req, timeout=timeout) as r:
                   return r.read()
           except HTTPError as e:
               if (e.code == 429 or 500 <= e.code <= 599) and attempt < max_retries:
                   time.sleep(backoff); attempt += 1; backoff *= 2; continue
               raise
           except URLError:
               if attempt < max_retries:
                   time.sleep(backoff); attempt += 1; backoff *= 2; continue
               raise
   
   def _safe_name(url: str) -> str:
       # Create a short, filesystem-safe token for the URL
       return url.replace("://", "_").replace("/", "_").replace("?", "_").replace("&", "_")[:100]
   
   def _put_csv(blob: bytes, url: str, run_ts: int, idx: int) -> str:
       key = f"{PREFIX}/{time.strftime('%Y/%m/%d/%H%M%S', time.gmtime(run_ts))}-url{idx:03d}-{_safe_name(url)}.csv"
       s3.put_object(
           Bucket=BUCKET,
           Key=key,
           Body=blob,
           ContentType="text/csv",
       )
       return key
   
   def lambda_handler(event=None, context=None):
       assert IOC_URLS, "IOC_URLS must contain at least one HTTPS URL"
       run_ts = int(time.time())
       written = []
       for i, url in enumerate(IOC_URLS):
           req = _build_request(url)
           data = _http_bytes(req)
           key = _put_csv(data, url, run_ts, i)
           written.append({"url": url, "s3_key": key, "bytes": len(data)})
       return {"ok": True, "written": written}
   
   if __name__ == "__main__":
       print(json.dumps(lambda_handler(), indent=2))
   

5. Go to Configuration > Environment variables > Edit > Add new environment variable.

6. Enter the following environment variables, replacing with your values:

   Key	Example
   S3_BUCKET	csv-ioc
   S3_PREFIX	csv-ioc/
   IOC_URLS	https://ioc.example.com/feed.csv,https://another.example.org/iocs.csv
   AUTH_HEADER	Authorization: Bearer <token>
   TIMEOUT	60

7. After the function is created, stay on its page (or open Lambda > Functions > your-function).

8. Select the Configuration tab.

9. In the General configuration panel click Edit.

10. Change Timeout to 5 minutes (300 seconds) and click Save.

Create an EventBridge schedule

1. Go to Amazon EventBridge > Scheduler > Create schedule.
2. Provide the following configuration details:
   • Recurring schedule: Rate (1 hour).
   • Target: your Lambda function.
   • Name: csv-custom-ioc-1h.
3. Click Create schedule.

Optional: Create read-only IAM user & keys for Google SecOps

1. In the AWS Console, go to IAM > Users, then click Add users.
2. Provide the following configuration details:
   • User: Enter a unique name (for example, secops-reader)
   • Access type: Select Access key - Programmatic access
   • Click Create user.
3. Attach minimal read policy (custom): Users > select secops-reader > Permissions > Add permissions > Attach policies directly > Create policy

4. In the JSON editor, enter the following policy:

   {
     "Version": "2012-10-17",
     "Statement": [
       {
         "Effect": "Allow",
         "Action": ["s3:GetObject"],
         "Resource": "arn:aws:s3:::<your-bucket>/*"
       },
       {
         "Effect": "Allow",
         "Action": ["s3:ListBucket"],
         "Resource": "arn:aws:s3:::<your-bucket>"
       }
     ]
   }
   

5. Set the name to secops-reader-policy.

6. Go to Create policy > search/select > Next > Add permissions.

7. Go to Security credentials > Access keys > Create access key.

8. Download the CSV (these values are entered into the feed).

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

1. Go to SIEM Settings > Feeds.
2. Click Add New Feed.
3. In the Feed name field, enter a name for the feed (for example, CSV Custom IOC).
4. Select Amazon S3 V2 as the Source type.
5. Select CSV Custom IOC as the Log type.
6. Click Next.
7. Specify values for the following input parameters:
   • S3 URI: s3://csv-ioc/csv-ioc/
   • Source deletion options: Select the deletion option according to your preference.
   • Maximum File Age: Default 180 Days.
   • Access Key ID: User access key with access to the S3 bucket.
   • Secret Access Key: User secret key with access to the S3 bucket.
   • Asset namespace: The asset namespace.
   • Ingestion labels: The label to be applied to the events from this feed.
8. Click Next.
9. Review your new feed configuration in the Finalize screen, and then click Submit.

UDM Mapping Table

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