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Potential Reverse Shell via Suspicious Child Process

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Potential Reverse Shell via Suspicious Child Process

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This detection rule detects the creation of a shell through a suspicious process chain. Any reverse shells spawned by the specified utilities that are initialized from a single process followed by a network connection attempt will be captured through this rule. Attackers may spawn reverse shells to establish persistence onto a target system.

Rule type: eql

Rule indices:

logs-endpoint.events.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Methodology%20and%20Resources/Reverse%20Shell%20Cheatsheet.md

Tags:

Domain: Endpoint
OS: Linux
Use Case: Threat Detection
Tactic: Execution
Data Source: Elastic Defend

Version: 6

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

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sequence by host.id, process.entity_id with maxspan=1s
  [process where host.os.type == "linux" and event.type == "start" and event.action in ("exec", "fork") and (
    (process.name : "python*" and process.args : "-c" and process.args : (
     "*import*pty*spawn*", "*import*subprocess*call*"
    )) or
    (process.name : "perl*" and process.args : "-e" and process.args : "*socket*" and process.args : (
     "*exec*", "*system*"
    )) or
    (process.name : "ruby*" and process.args : ("-e", "-rsocket") and process.args : (
     "*TCPSocket.new*", "*TCPSocket.open*"
     )) or
    (process.name : "lua*" and process.args : "-e" and process.args : "*socket.tcp*" and process.args : (
     "*io.popen*", "*os.execute*"
    )) or
    (process.name : "php*" and process.args : "-r" and process.args : "*fsockopen*" and process.args : "*/bin/*sh*") or
    (process.name : ("awk", "gawk", "mawk", "nawk") and process.args : "*/inet/tcp/*") or
    (process.name : "openssl" and process.args : "-connect") or
    (process.name : ("nc", "ncat", "netcat") and process.args_count >= 3 and not process.args == "-z") or
    (process.name : "telnet" and process.args_count >= 3)
  ) and process.parent.name : (
    "bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish", "python*", "php*", "perl", "ruby", "lua*",
    "openssl", "nc", "netcat", "ncat", "telnet", "awk")]
  [network where host.os.type == "linux" and event.type == "start" and event.action in ("connection_attempted", "connection_accepted") and
    process.name : ("python*", "php*", "perl", "ruby", "lua*", "openssl", "nc", "netcat", "ncat", "telnet", "awk") and
    destination.ip != null and not cidrmatch(destination.ip, "127.0.0.0/8", "169.254.0.0/16", "224.0.0.0/4", "::1")]

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
Technique:
- Name: Command and Scripting Interpreter
- ID: T1059
- Reference URL: https://attack.mitre.org/techniques/T1059/
Sub-technique:
- Name: Unix Shell
- ID: T1059.004
- Reference URL: https://attack.mitre.org/techniques/T1059/004/
Tactic:
- Name: Command and Control
- ID: TA0011
- Reference URL: https://attack.mitre.org/tactics/TA0011/
Technique:
- Name: Application Layer Protocol
- ID: T1071
- Reference URL: https://attack.mitre.org/techniques/T1071/

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