Anthropic Activity from a Suspicious User Agent

[metadata]
creation_date = "2026/09/16"
integration = ["anthropic"]
maturity = "production"
updated_date = "2026/09/21"

[rule]
author = ["Elastic"]
description = """
Detects successful Anthropic audit activity where the user agent matches scripting HTTP clients, offensive scanners,
or automation libraries (for example curl, python-requests, Go-http-client, axios, nuclei). Browser and first-party
Claude clients normally present recognizable browser or product user agents; raw HTTP library agents on successful
control-plane or product activity often indicate scripted access, stolen-session reuse, or unauthorized automation.
Known benign automation patterns (axios or Go HTTP clients on file upload/delete, trusted device enrollment, and
environment creation) are excluded.
"""
false_positives = [
    """
    Approved internal automation, CI jobs, or SDK integrations may present scripting user agents. Validate the actor,
    source IP, and action against change tickets before treating as compromise. Prefer excluding stable identities or
    source networks rather than removing the matching user-agent pattern.
    """,
    """
    Penetration tests and red-team exercises that use curl, httpx, or similar clients will match. Add temporary
    exceptions for the engagement window after validation.
    """,
]
from = "now-9m"
language = "esql"
license = "Elastic License v2"
name = "Anthropic Activity from a Suspicious User Agent"
note = """## Triage and analysis

### Investigating Anthropic Activity from a Suspicious User Agent

Successful Anthropic audit events normally come from browser or first-party Claude clients. This rule flags scripting
HTTP clients, scanners, or automation libraries on successful activity. UAs are spoofable — corroborate with actor,
IP, and `event.action`.

Benign automation using axios or Go HTTP clients is already excluded for `platform_file_uploaded`,
`platform_file_deleted`, `claude_file_uploaded`, `trusted_device_enrolled`, and `environment_created`.

Unauthorized / escalate when a normally browser-bound user suddenly uses curl/python/Go-http-client on privileged
actions (IAM, exports, SSO, keys). Close as FP for approved SDK/CI identities on expected actions.

#### Possible investigation steps

- Compare `user_agent.original` and `event.action` to the user's baseline. A shift to curl, python-requests, or
  Go-http-client on admin/export actions is higher priority than the same UA on already-allowlisted file ops.
- Branch `anthropic.audit.actor.type` and check `user.email` / `source.ip` against approved automation inventory.
- Pivot the same email/IP for auth failures, impossible travel, role changes, exports, or compliance logging changes.

### False positive analysis

- Internal GenAI SDKs (`openai*`, `anthropic-sdk*`, `langchain*`) and CI jobs match — exclude stable identities, not
  entire UA families. Extend the Go/axios action allowlist only with evidence of additional benign actions.

### Response and remediation

- On unauthorized scripting access: revoke sessions, rotate credentials/MFA, review admin/export activity around the
  alert, and hunt other scripting-UA activity from the same IP or email.
"""
references = [
    "https://platform.claude.com/docs/en/api/compliance/activities/list",
]
risk_score = 47
rule_id = "d370aacb-a344-4578-a69c-beca88e063a1"
severity = "medium"
tags = [
    "Domain: GenAI",
    "Platform: Anthropic",
    "Data Source: Anthropic Audit Logs",
    "Use Case: Threat Detection",
    "Resources: Investigation Guide",
    "Rule Type: ES|QL",
    "Tactic: Command and Control",
]
timestamp_override = "event.ingested"
type = "esql"

query = '''
from logs-anthropic.audit-* metadata _id, _version, _index
| where
    data_stream.dataset == "anthropic.audit" and
    event.outcome == "success" and
    source.ip is not null and
    source.ip != "0.0.0.0" and
    user.email is not null and
    user_agent.original is not null
| eval Esql.ua_lower = to_lower(user_agent.original)
| where
    (
        Esql.ua_lower like "curl*" or
        Esql.ua_lower like "python*" or
        Esql.ua_lower like "wget*" or
        Esql.ua_lower like "go-http*" or
        Esql.ua_lower like "perl*" or
        Esql.ua_lower like "libwww-perl*" or
        Esql.ua_lower like "java*" or
        Esql.ua_lower like "node*" or
        Esql.ua_lower like "php*" or
        Esql.ua_lower like "guzzle*" or
        Esql.ua_lower like "bun*" or
        Esql.ua_lower like "axios*" or
        Esql.ua_lower like "undici*" or
        Esql.ua_lower like "okhttp*" or
        Esql.ua_lower like "apache-httpclient*" or
        Esql.ua_lower like "httpclient*" or
        Esql.ua_lower like "httpie*" or
        Esql.ua_lower like "ruby*" or
        Esql.ua_lower like "postmanruntime*" or
        Esql.ua_lower like "restsharp*" or
        Esql.ua_lower like "*kali*" or
        Esql.ua_lower like "*parrot*" or
        Esql.ua_lower like "*pentoo*" or
        Esql.ua_lower like "*backbox*" or
        Esql.ua_lower like "*blackarch*" or
        Esql.ua_lower like "scrapy*" or
        Esql.ua_lower like "mechanize*" or
        Esql.ua_lower like "aiohttp*" or
        Esql.ua_lower like "httpx*" or
        Esql.ua_lower like "requests*" or
        Esql.ua_lower like "pycurl*" or
        Esql.ua_lower like "urllib*" or
        Esql.ua_lower like "got/*" or
        Esql.ua_lower like "node-fetch*" or
        Esql.ua_lower like "superagent*" or
        Esql.ua_lower like "ky/*" or
        Esql.ua_lower like "fetch*" or
        Esql.ua_lower like "deno*" or
        Esql.ua_lower like "powershell*" or
        Esql.ua_lower like "invoke-webrequest*" or
        Esql.ua_lower like "windowspowershell*" or
        Esql.ua_lower like "wget2*" or
        Esql.ua_lower like "aria2*" or
        Esql.ua_lower like "httrack*" or
        Esql.ua_lower like "nikto*" or
        Esql.ua_lower like "sqlmap*" or
        Esql.ua_lower like "nmap*" or
        Esql.ua_lower like "masscan*" or
        Esql.ua_lower like "zgrab*" or
        Esql.ua_lower like "nuclei*" or
        Esql.ua_lower like "dirbuster*" or
        Esql.ua_lower like "gobuster*" or
        Esql.ua_lower like "ffuf*" or
        Esql.ua_lower like "feroxbuster*" or
        Esql.ua_lower like "wfuzz*" or
        Esql.ua_lower like "burpsuite*" or
        Esql.ua_lower like "hydra*" or
        Esql.ua_lower like "metasploit*" or
        Esql.ua_lower like "*havoc*" or
        Esql.ua_lower like "*sliver*" or
        Esql.ua_lower like "*cobalt strike*" or
        Esql.ua_lower like "dart*" or
        Esql.ua_lower like "rector*" or
        Esql.ua_lower like "ruby-faraday*" or
        Esql.ua_lower like "httparty*" or
        Esql.ua_lower like "clj-http*" or
        Esql.ua_lower like "hackney*" or
        Esql.ua_lower like "elixir*" or
        Esql.ua_lower like "swift-nio*" or
        Esql.ua_lower like "vapor*" or
        Esql.ua_lower like "rust*" or
        Esql.ua_lower like "reqwest*" or
        Esql.ua_lower like "ureq*" or
        Esql.ua_lower like "hyper/*" or
        Esql.ua_lower like "cohere-go*" or
        Esql.ua_lower like "openai*" or
        Esql.ua_lower like "anthropic-sdk*" or
        Esql.ua_lower like "langchain*" or
        Esql.ua_lower like "llamaindex*" or
        Esql.ua_lower like "litellm*" or
        Esql.ua_lower like "dspy*" or
        Esql.ua_lower like "*zgrab*" or
        Esql.ua_lower like "*masscan*" or
        Esql.ua_lower like "*nessus*" or
        Esql.ua_lower like "*shodan*" or
        Esql.ua_lower like "*censys*" or
        Esql.ua_lower like "*binaryedge*" or
        Esql.ua_lower like "*internetmeasurement*" or
        Esql.ua_lower like "*internetcensus*" or
        Esql.ua_lower like "*shadowserver*" or
        Esql.ua_lower like "*stretchoid*" or
        Esql.ua_lower like "*http.rb*"
    ) and
    not (
        event.action in (
            "platform_file_deleted",
            "platform_file_uploaded",
            "claude_file_uploaded",
            "trusted_device_enrolled",
            "environment_created"
        ) and
        (Esql.ua_lower like "go-http*" or Esql.ua_lower like "axios*")
    )
| keep _id, _version, _index, @timestamp, event.*, organization.*, user.*, source.*, user_agent.*, anthropic.audit.*, data_stream.*, Esql.ua_lower
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1071"
name = "Application Layer Protocol"
reference = "https://attack.mitre.org/techniques/T1071/"
[[rule.threat.technique.subtechnique]]
id = "T1071.001"
name = "Web Protocols"
reference = "https://attack.mitre.org/techniques/T1071/001/"


[rule.threat.tactic]
id = "TA0011"
name = "Command and Control"
reference = "https://attack.mitre.org/tactics/TA0011/"

[rule.alert_suppression]
group_by = ["user.email", "source.ip", "user_agent.original"]
duration = {value = 1, unit = "h"}
missing_fields_strategy = "suppress"

[rule.investigation_fields]
field_names = [
    "@timestamp",
    "event.action",
    "event.id",
    "event.outcome",
    "organization.id",
    "user.email",
    "user.id",
    "source.ip",
    "user_agent.original",
    "anthropic.audit.actor.type",
    "Esql.ua_lower",
]