The hypothesis is that the detection rule identifies potential BlackEnergy / Voodoo Bear implant activity by APT28, characterized by suspicious process execution and network communication patterns indicative of command and control. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate advanced persistent threats before they cause significant damage to critical infrastructure.
YARA Rule
rule IMPLANT_4_v10 {
meta:
description = "BlackEnergy / Voodoo Bear Implant by APT28"
author = "US CERT"
reference = "https://www.us-cert.gov/ncas/current-activity/2017/02/10/Enhanced-Analysis-GRIZZLY-STEPPE"
date = "2017-02-10"
score = 85
strings:
$ ={A1B05C72}
$ ={EB3D0384}
$ ={6F45594E}
$ ={71815A4E}
$ ={D5B03E72}
$ ={6B43594E}
$ ={F572993D}
$ ={665D9DC0}
$ ={0BE7A75A}
$ ={F37443C5}
$ ={A2A474BB}
$ ={97DEEC67}
$ ={7E0CB078}
$ ={9C9678BF}
$ ={4A37A149}
$ ={8667416B}
$ ={0A375BA4}
$ ={DC505A8D}
$ ={02F1F808}
$ ={2C819712}
condition:
uint16(0) == 0x5A4D and uint16(uint32(0x3c)) == 0x4550 and 15 of them
}This YARA rule can be deployed in the following contexts:
Scenario: Scheduled System Maintenance Task
Description: A legitimate system maintenance task, such as schtasks.exe running a scheduled job to clean temporary files or update system settings.
Filter/Exclusion: Check for process.name = schtasks.exe and process.command_line containing /create or /run with known maintenance scripts. Exclude tasks with task_name matching enterprise-defined maintenance schedules.
Scenario: Admin User Performing Remote Desktop Session
Description: An admin user using mstsc.exe (Remote Desktop Connection) to access a remote server, which may trigger network activity similar to C2 traffic.
Filter/Exclusion: Filter by process.name = mstsc.exe and check for user.name in the admin group. Exclude connections to internal IP ranges or known admin servers.
Scenario: PowerShell Script for System Monitoring
Description: A legitimate PowerShell script, such as PowerShell.exe running a script to monitor system performance or log file integrity.
Filter/Exclusion: Check for process.name = powershell.exe and process.command_line containing -File or -Command with known monitoring scripts. Exclude scripts located in enterprise monitoring directories (e.g., C:\Monitoring\).
Scenario: Antivirus or EDR Tool Performing Full System Scan
Description: A security tool like Microsoft Defender or CrowdStrike Falcon performing a full system scan, which may generate network traffic or file modifications.
Filter/Exclusion: Filter by process.name matching the EDR/AV tool name and check for process.command_line containing scan-related arguments (e.g., /fullscan, /scan). Exclude processes with process.parent.name matching the EDR/AV service.
**Scenario: Database Backup Job