Gafgyt Trojan

Hunt Hypothesis

The Gafgyt Trojan is detected through unusual network traffic patterns indicative of command and control communication. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential botnet activity early.

YARA Rule

rule Gafgyt_Botnet_HIHI: MALW
{
meta:
description = "Gafgyt Trojan"
author = "Joan Soriano / @joanbtl"
date = "2017-05-01"
version = "1.0"
MD5 = "cc99e8dd2067fd5702a4716164865c8a"
SHA1 = "b9b316c1cc9f7a1bf8c70400861de08d95716e49"

    strings:
            $s1 = "PING"
            $s2 = "PONG"
            $s3 = "TELNET LOGIN CRACKED - %s:%s:%s"
            $s4 = "ADVANCEDBOT"
            $s5 = "46.166.185.92"
            $s6 = "LOLNOGTFO"

    condition:
            $s1 and $s2 and $s3 and $s4 and $s5 and $s6
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 6 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Legitimate scheduled job running a known Gafgyt variant for testing purposes
  Filter/Exclusion: process.name != "gafgyt-test-tool" or process.args contains "test-mode"

• Scenario: System update or patching process that includes a Gafgyt-related binary (e.g., during a security tool installation)
  Filter/Exclusion: process.name contains "update" or process.parent.name contains "setup.exe"

• Scenario: Admin task using a legitimate tool that has a similar name to Gafgyt (e.g., gafgyt is part of a legitimate network diagnostic tool)
  Filter/Exclusion: process.name contains "network-diag" or process.parent.name contains "admin-tools"

• Scenario: False positive from a security tool’s own binary that matches Gafgyt signatures (e.g., during a scan or analysis)
  Filter/Exclusion: process.name contains "security-tool" or process.parent.name contains "scan-engine"

• Scenario: Legitimate script or job that uses a Gafgyt-like name for internal logging or monitoring purposes
  Filter/Exclusion: process.name contains "log-monitor" or process.args contains "internal-use"