macOS: nscurl File Download via Command-Line Options

title: "macOS: nscurl File Download via Command-Line Options"
id: 4aceaad4-16c2-4a3b-825d-b1ab1caf498c
status: test
description: This rule identifies process executions of the nscurl utility on macOS where the command line includes file download-related flags (for example, --download, --download-directory, --output, -dir, -dl, -ld, or -o). Attackers may use nscurl to fetch remote content as part of command-and-control or staging activity. Telemetry relies on macOS process creation records capturing the executable path and full command line arguments.
references:
  - https://www.loobins.io/binaries/nscurl/
  - https://www.agnosticdev.com/content/how-diagnose-app-transport-security-issues-using-nscurl-and-openssl
  - https://gist.github.com/nasbench/ca6ef95db04ae04ffd1e0b1ce709cadd
  - https://github.com/SigmaHQ/sigma/blob/master/rules/macos/process_creation/proc_creation_macos_nscurl_usage.yml
author: Daniel Cortez, Huntrule Team
date: 2024-06-04
tags:
  - attack.command-and-control
  - attack.t1105
logsource:
  category: process_creation
  product: macos
detection:
  selection:
    Image|endswith: /nscurl
    CommandLine|contains:
      - "--download "
      - "--download-directory "
      - "--output "
      - "-dir "
      - "-dl "
      - -ld
      - "-o "
  condition: selection
falsepositives:
  - Legitimate usage of nscurl by administrators and users.
level: medium
license: DRL-1.1
related:
  - id: 6d8a7cf1-8085-423b-b87d-7e880faabbdf
    type: derived