PUA - Netcat Suspicious Execution

SIGMA detection rule by frack113, Florian Roth (Nextron Systems) · GPL-2.0

Detects execution of Netcat. Adversaries may use a non-application layer protocol for communication between host and C2 server or among infected hosts within a network

title: PUA - Netcat Suspicious Execution
id: f483b0b8-2606-8691-2edb-5c64c3a7347e
related:
    - id: e31033fc-33f0-4020-9a16-faf9b31cbf08
      type: derived
status: test
description: Detects execution of Netcat. Adversaries may use a non-application layer protocol for communication between host and C2 server or among infected hosts within a network
references:
    - https://nmap.org/ncat/
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1095/T1095.md
    - https://www.revshells.com/
author: frack113, Florian Roth (Nextron Systems)
date: 2021-07-21
modified: 2023-02-08
tags:
    - attack.command-and-control
    - attack.t1095
logsource:
    category: process_creation
    product: windows
detection:
    process_creation:
        EventID: 4688
        Channel: Security
    selection_img:
        # can not use OriginalFileName as is empty
        NewProcessName|endswith:
            - \nc.exe
            - \ncat.exe
            - \netcat.exe
    selection_cmdline:
        # Typical command lines
        CommandLine|contains:
            - ' -lvp '
            - ' -lvnp'
            - ' -l -v -p '
            - ' -lv -p '
            - ' -l --proxy-type http '
            # - ' --exec cmd.exe ' # Not specific enough for netcat
            - ' -vnl --exec '
            - ' -vnl -e '
            - ' --lua-exec '
            - ' --sh-exec '
    condition: process_creation and (1 of selection_*)
falsepositives:
    - Legitimate ncat use
level: high
ruletype: Sigma

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

43a6dce8-5f64-4b33-a020-09c2d80562bd

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

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