rules/integrations/aws/impact_s3_static_site_js_file_uploaded.toml

[metadata]
creation_date = "2025/04/15"
integration = ["aws"]
maturity = "production"
updated_date = "2025/04/15"

[rule]
author = ["Elastic"]
description = """
This rule detects when a JavaScript file is uploaded or accessed in an S3 static site directory (`static/js/`) by an IAM
user or assumed role. This can indicate suspicious modification of web content hosted on S3, such as injecting malicious scripts into a
static website frontend.
"""
false_positives = [
    """
    Development or deployment pipelines that update static frontends frequently (e.g., React/Vue apps) may trigger this.
    Verify the user agent, source IP, and whether the modification was expected.
    """,
]
from = "now-9m"
language = "esql"
license = "Elastic License v2"
name = "AWS S3 Static Site JavaScript File Uploaded"
note = """## Triage and Analysis

### Investigating AWS S3 Static Site JavaScript File Uploaded

An S3 `PutObject` action that targets a path like `static/js/` and uploads a `.js` file is a potential signal for web content modification. If done by an unexpected IAM user or outside of CI/CD workflows, it may indicate a compromise.

#### Possible Investigation Steps

- **Identify the Source User**: Check `aws.cloudtrail.user_identity.arn`, access key ID, and session type (`IAMUser`, `AssumedRole`, etc).
- **Review File Content**: Use the S3 `GetObject` or CloudTrail `requestParameters` to inspect the uploaded file for signs of obfuscation or injection.
- **Correlate to Other Events**: Review events from the same IAM user before and after the upload (e.g., `ListBuckets`, `GetCallerIdentity`, IAM activity).
- **Look for Multiple Uploads**: Attackers may attempt to upload several files or modify multiple directories.

### False Positive Analysis

- This behavior may be expected during app deployments. Look at:
  - The `user_agent.original` to detect legitimate CI tools (like Terraform or GitHub Actions).
  - Timing patterns—does this match a regular release window?
  - The origin IP and device identity.

### Response and Remediation

- **Revert Malicious Code**: Replace the uploaded JS file with a clean version and invalidate CloudFront cache if applicable.
- **Revoke Access**: If compromise is confirmed, revoke the IAM credentials and disable the user.
- **Audit IAM Policies**: Ensure that only deployment users can modify static site buckets.
- **Enable Bucket Versioning**: This can allow for quick rollback and historical review.
"""
references = [
    "https://www.sygnia.co/blog/sygnia-investigation-bybit-hack/",
    "https://docs.aws.amazon.com/AmazonS3/latest/userguide/WebsiteHosting.html",
    "https://docs.aws.amazon.com/AmazonS3/latest/API/API_PutObject.html",
]
risk_score = 47
rule_id = "16acac42-b2f9-4802-9290-d6c30914db6e"
severity = "medium"
tags = [
    "Domain: Cloud",
    "Data Source: AWS",
    "Data Source: Amazon Web Services",
    "Data Source: AWS S3",
    "Tactic: Impact",
    "Use Case: Web Application Compromise",
    "Use Case: Cloud Threat Detection",
    "Resources: Investigation Guide",
]
timestamp_override = "event.ingested"
type = "esql"

query = '''
from logs-aws.cloudtrail* metadata _id, _version, _index
| where

    // filter on CloudTrail logs for S3 PutObject actions
    event.dataset == "aws.cloudtrail"
    and event.provider == "s3.amazonaws.com"
    and event.action in ("GetObject","PutObject")

    // filter for IAM users, not federated identities
    and aws.cloudtrail.user_identity.type in ("IAMUser", "AssumedRole")

    // filter for S3 static site bucket paths from webpack or similar
    and aws.cloudtrail.request_parameters LIKE "*static/js/*.js*"

    // exclude common IaC tools and automation scripts
    and not (
        user_agent.original LIKE "*Terraform*"
        or user_agent.original LIKE "*Ansible*"
        or user_agent.original LIKE "*Pulumni*"
    )

// extract bucket and object details from request parameters
| dissect aws.cloudtrail.request_parameters "%{{?bucket.name.key}=%{bucket.name}, %{?host.key}=%{bucket.host}, %{?bucket.object.location.key}=%{bucket.object.location}}"

// filter for specific bucket and object structure
| dissect bucket.object.location "%{}static/js/%{bucket.object}"

// filter for JavaScript files
| where ENDS_WITH(bucket.object, ".js")
| keep
    aws.cloudtrail.user_identity.arn,
    aws.cloudtrail.user_identity.access_key_id,
    aws.cloudtrail.user_identity.type,
    aws.cloudtrail.request_parameters,
    bucket.name,
    bucket.object,
    user_agent.original,
    source.ip,
    event.action,
    @timestamp
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1565"
name = "Data Manipulation"
reference = "https://attack.mitre.org/techniques/T1565/"
[[rule.threat.technique.subtechnique]]
id = "T1565.001"
name = "Stored Data Manipulation"
reference = "https://attack.mitre.org/techniques/T1565/001/"



[rule.threat.tactic]
id = "TA0040"
name = "Impact"
reference = "https://attack.mitre.org/tactics/TA0040/"