sigma-rules/rules/windows/execution_susp_javascript_via_deno.toml

[metadata]
creation_date = "2026/03/19"
integration = ["endpoint", "windows", "sentinel_one_cloud_funnel", "m365_defender", "system", "crowdstrike"]
maturity = "production"
updated_date = "2026/04/07"

[rule]
author = ["Elastic"]
description = """
Detects execution of JavaScript via Deno with suspicious command-line patterns (base64, eval, http, or import in a
javascript context). Adversaries may abuse Deno to run malicious JavaScript for execution or staging.
"""
from = "now-9m"
index = [
    "endgame-*",
    "logs-crowdstrike.fdr*",
    "logs-endpoint.events.process-*",
    "logs-m365_defender.event-*",
    "logs-sentinel_one_cloud_funnel.*",
    "logs-system.security*",
    "logs-windows.sysmon_operational-*",
    "winlogbeat-*",
]
language = "eql"
license = "Elastic License v2"
name = "Suspicious JavaScript Execution via Deno"
note = """## Triage and analysis

### Investigating Suspicious JavaScript Execution via Deno

Deno is a legitimate JavaScript/TypeScript runtime. This rule fires when a Deno process (identified by name, PE original filename, or code signer "Deno Land Inc.") is started with a command line matching suspicious patterns: javascript with base64, eval(, http, or javascript import. Such patterns are commonly used to run inline or remote scripts and can indicate abuse.

### Possible investigation steps

- Review process.command_line and process.args to see the exact script or URL being executed.
- Identify the parent process and how Deno was launched (user, script, terminal, or other tool).
- Check whether Deno is approved on the host; if not, treat as potential unauthorized software execution.
- Correlate with file creation or network events around the same time (downloads, script drops).

### False positive analysis

- Legitimate development or automation that runs Deno with eval, http imports, or base64-encoded snippets may trigger; allowlist by host or command-line pattern where appropriate.

### Response and remediation

- If abuse is confirmed: contain the host, terminate the Deno process, and remove or block Deno if not authorized; investigate how the script was delivered and scope for similar activity.
"""
references = [
    "https://reliaquest.com/blog/threat-spotlight-casting-a-wider-net-clickfix-deno-and-leaknets-scaling-threat",
    "https://deno.com/"
]
risk_score = 73
rule_id = "ff18d24b-2ba6-4691-a17f-75c4380d0965"
severity = "high"
tags = [
    "Domain: Endpoint",
    "OS: Windows",
    "Use Case: Threat Detection",
    "Tactic: Execution",
    "Resources: Investigation Guide",
    "Data Source: Elastic Defend",
    "Data Source: Sysmon",
    "Data Source: SentinelOne",
    "Data Source: Microsoft Defender XDR",
    "Data Source: Crowdstrike",
    "Data Source: Elastic Endgame", 
    "Data Source: Windows Security Event Logs"
]
timestamp_override = "event.ingested"
type = "eql"

query = '''
process where host.os.type == "windows" and event.type == "start" and
 (process.name : "deno.exe" or ?process.pe.original_file_name == "deno.exe" or ?process.code_signature.subject_name == "Deno Land Inc.") and
 process.command_line : ("*javascript*base64*", "*eval(*", "*http*", "*javascript*import*")
'''

[[rule.threat]]
framework = "MITRE ATT&CK"

[[rule.threat.technique]]
id = "T1059"
name = "Command and Scripting Interpreter"
reference = "https://attack.mitre.org/techniques/T1059/"

[[rule.threat.technique.subtechnique]]
id = "T1059.007"
name = "JavaScript"
reference = "https://attack.mitre.org/techniques/T1059/007/"

[rule.threat.tactic]
id = "TA0002"
name = "Execution"
reference = "https://attack.mitre.org/tactics/TA0002/"

[[rule.threat]]
framework = "MITRE ATT&CK"

[[rule.threat.technique]]
id = "T1105"
name = "Ingress Tool Transfer"
reference = "https://attack.mitre.org/techniques/T1105/"

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

[[rule.threat]]
framework = "MITRE ATT&CK"

[[rule.threat.technique]]
id = "T1027"
name = "Obfuscated Files or Information"
reference = "https://attack.mitre.org/techniques/T1027/"

[rule.threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"