The detection identifies potential exploitation of the leaked Equation Group tool ‘estesfox’ by adversaries attempting to execute malicious code within a network. SOC teams should proactively hunt for this behavior to identify and mitigate early-stage advanced persistent threat activity leveraging compromised tools.
YARA Rule
rule EquationGroup_estesfox {
meta:
description = "Equation Group hack tool leaked by ShadowBrokers- file estesfox"
author = "Florian Roth"
reference = "https://medium.com/@shadowbrokerss/dont-forget-your-base-867d304a94b1"
date = "2017-04-08"
hash1 = "33530cae130ee9d9deeee60df9292c00242c0fe6f7b8eedef8ed09881b7e1d5a"
strings:
$x1 = "chown root:root x;chmod 4777 x`' /tmp/logwatch.$2/cron" fullword ascii
condition:
all of them
}
This YARA rule can be deployed in the following contexts:
This rule contains 1 string patterns in its detection logic.
Scenario: Legitimate System File Update
Description: A system update or patch deployment includes a file named estesfox.exe as part of a legitimate software update.
Filter/Exclusion: Check the file’s hash against known good hashes from the vendor or use a file integrity monitoring tool to differentiate between legitimate and malicious updates.
Scenario: Scheduled Job Execution
Description: A scheduled task or job (e.g., Task Scheduler or cron job) runs a script or tool named estesfox.exe as part of a routine maintenance or data processing task.
Filter/Exclusion: Filter by process owner (e.g., SYSTEM, LocalService, or a known service account) or check the command line arguments for expected job parameters.
Scenario: Antivirus or Security Tool Scan
Description: A security tool or antivirus software (e.g., Malwarebytes, Bitdefender) uses a tool named estesfox.exe as part of its scanning or analysis process.
Filter/Exclusion: Check the process tree for parent processes associated with known security tools, or use a file signature check to confirm the tool’s legitimacy.
Scenario: Network Monitoring Tool Usage
Description: A network monitoring or packet analysis tool (e.g., Wireshark, tcpdump) includes a utility named estesfox.exe for internal diagnostics or logging.
Filter/Exclusion: Filter by process name or use a whitelist of known network tools. Verify the file’s location in standard tool directories (e.g., C:\Program Files\Wireshark\).
Scenario: Custom Script or Automation Tool
Description: A custom script or automation tool (e.g., PowerShell, Python, or Batch) includes a utility named estesfox.exe for