Kalambur Backdoor Curl TOR SOCKS Proxy Execution

SIGMA detection rule by Arda Buyukkaya (EclecticIQ) · NOASSERTION

Detects the execution of the "curl.exe" command, referencing "SOCKS" and ".onion" domains, which could be indicative of Kalambur backdoor activity.

title: Kalambur Backdoor Curl TOR SOCKS Proxy Execution
id: e99375eb-3ee0-407a-9f90-79569cc6a01c
status: experimental
description: Detects the execution of the "curl.exe" command, referencing "SOCKS" and ".onion" domains, which could be indicative of Kalambur backdoor activity.
references:
    - https://blog.eclecticiq.com/sandworm-apt-targets-ukrainian-users-with-trojanized-microsoft-kms-activation-tools-in-cyber-espionage-campaigns
author: Arda Buyukkaya (EclecticIQ)
date: 2025-02-11
tags:
    - attack.execution
    - attack.command-and-control
    - attack.t1090
    - attack.t1573
    - attack.t1071.001
    - attack.t1059.001
    - attack.s0183
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        Image|endswith: '\curl.exe'
    selection_socks:
        CommandLine|contains:
            - 'socks5h://'
            - 'socks5://'
            - 'socks4a://'
    selection_onion:
        CommandLine|contains: '.onion'
    condition: all of selection_*
falsepositives:
    - Unlikely
level: high

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

d92ef18c-942e-47ef-910d-aff38e3f81f0

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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