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Potential Reverse Shell via Suspicious Binary

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Potential Reverse Shell via Suspicious Binary

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This detection rule detects the creation of a shell through a chain consisting of the execution of a suspicious binary (located in a commonly abused location or executed manually) followed by a network event and ending with a shell being spawned. Stageless reverse tcp shells display this behaviour. 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: 5

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 == "exec" and
  process.executable : (
  "./*", "/tmp/*", "/var/tmp/*", "/var/www/*", "/dev/shm/*", "/etc/init.d/*", "/etc/rc*.d/*",
  "/etc/crontab", "/etc/cron.*", "/etc/update-motd.d/*", "/usr/lib/update-notifier/*",
  "/boot/*", "/srv/*", "/run/*", "/root/*", "/etc/rc.local"
   ) and
  process.parent.name : ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") and not
  process.name : ("curl", "wget", "ping", "apt", "dpkg", "yum", "rpm", "dnf", "dockerd") ]
[ network where host.os.type == "linux" and event.type == "start" and event.action in ("connection_attempted", "connection_accepted") and
  process.executable : (
  "./*", "/tmp/*", "/var/tmp/*", "/var/www/*", "/dev/shm/*", "/etc/init.d/*", "/etc/rc*.d/*",
  "/etc/crontab", "/etc/cron.*", "/etc/update-motd.d/*", "/usr/lib/update-notifier/*",
  "/boot/*", "/srv/*", "/run/*", "/root/*", "/etc/rc.local"
   ) and destination.ip != null and destination.ip != "127.0.0.1" and destination.ip != "::1" ]
[ process where host.os.type == "linux" and event.action == "exec" and event.type == "start" and
  process.name : ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") and
  process.parent.name : ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") ]

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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