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Detection rules › Sigma

File Download Via Nscurl - MacOS

Status
test
Severity
medium
Log source
category process_creation, product macos
Author
Daniel Cortez
Source
github.com/SigmaHQ/sigma

Detects the execution of the nscurl utility in order to download files.

Known false positives

  • Legitimate usage of nscurl by administrators and users.

MITRE ATT&CK coverage

TacticTechniques
Command & Control

Telemetry coverage

PlatformRecord / event type
macOSESF event exec (NOTIFY): Fires after execve(2) or posix_spawn(2) succeeds, delivering a post-fact record of the new process.

Rule body

title: File Download Via Nscurl - MacOS
id: 6d8a7cf1-8085-423b-b87d-7e880faabbdf
status: test
description: Detects the execution of the nscurl utility in order to download files.
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
author: Daniel Cortez
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

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith: '/nscurl'
    CommandLine|contains:
        - '--download '
        - '--download-directory '
        - '--output '
        - '-dir '
        - '-dl '
        - '-ld'
        - '-o '

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
CommandLinematch
  • --download
  • --download-directory
  • --output
  • -dir
  • -dl
  • -ld
  • -o
field:"CommandLine" kind:match
Imageends_with
  • /nscurl
field:"Image" kind:ends_with value:"/nscurl"