UNC4841 - Download Tar File From Untrusted Direct IP Via Wget

Detects execution of "wget" to download a "tar" from an IP address that doesn't have a trusted certificate. As seen used by UNC4841 during their Barracuda ESG zero day exploitation.

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Detection logic

selection

Image|endswith: /wget
CommandLine|re: https://[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}
CommandLine|contains: --no-check-certificate
CommandLine|endswith: .tar

filter_main_local_ips

CommandLine|contains:
  - https://10.
  - https://192.168.
  - https://172.16.
  - https://172.17.
  - https://172.18.
  - https://172.19.
  - https://172.20.
  - https://172.21.
  - https://172.22.
  - https://172.23.
  - https://172.24.
  - https://172.25.
  - https://172.26.
  - https://172.27.
  - https://172.28.
  - https://172.29.
  - https://172.30.
  - https://172.31.
  - https://127.
  - https://169.254.

Condition

selection and not 1 of filter_main_*

Raw YAML

title: UNC4841 - Download Tar File From Untrusted Direct IP Via Wget
id: 23835beb-ec38-4e74-a5d4-b99af6684e91
status: test
description: Detects execution of "wget" to download a "tar" from an IP address that doesn't have a trusted certificate. As seen used by UNC4841 during their Barracuda ESG zero day exploitation.
references:
    - https://www.mandiant.com/resources/blog/barracuda-esg-exploited-globally
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-06-16
tags:
    - attack.stealth
    - attack.t1140
    - detection.emerging-threats
logsource:
    product: linux
    category: process_creation
detection:
    selection:
        Image|endswith: '/wget'
        CommandLine|re: 'https://[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'
        CommandLine|contains: '--no-check-certificate'
        CommandLine|endswith: '.tar'
    filter_main_local_ips:
        # Note: Uncomment this filter if you want to exclude local IPs
        CommandLine|contains:
            - 'https://10.' # 10.0.0.0/8
            - 'https://192.168.' # 192.168.0.0/16
            - 'https://172.16.' # 172.16.0.0/12
            - 'https://172.17.'
            - 'https://172.18.'
            - 'https://172.19.'
            - 'https://172.20.'
            - 'https://172.21.'
            - 'https://172.22.'
            - 'https://172.23.'
            - 'https://172.24.'
            - 'https://172.25.'
            - 'https://172.26.'
            - 'https://172.27.'
            - 'https://172.28.'
            - 'https://172.29.'
            - 'https://172.30.'
            - 'https://172.31.'
            - 'https://127.' # 127.0.0.0/8
            - 'https://169.254.' # 169.254.0.0/16
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high