The hypothesis is that the detection rule identifies potential BlackEnergy / Voodoo Bear implant activity by APT28, characterized by suspicious file 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_v9 {
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:
$a = "wevtutil clear-log" ascii wide nocase
$b = "vssadmin delete shadows" ascii wide nocase
$c = "AGlobal\\23d1a259-88fa-41df-935f-cae523bab8e6" ascii wide nocase
$d = "Global\\07fd3ab3-0724-4cfd-8cc2-60c0e450bb9a" ascii wide nocase //$e = {57 55 33 c9 51 8b c3 99 57 52 50}
$openPhysicalDiskOverwriteWithZeros = { 57 55 33 C9 51 8B C3 99 57 52
50 E8 ?? ?? ?? ?? 52 50 E8 ?? ?? ?? ?? 83 C4 10 84 C0 75 21 33 C0 89
44 24 10 89 44 24 14 6A 01 8B C7 99 8D 4C 24 14 51 52 50 56 FF 15 ??
?? ?? ?? 85 C0 74 0B 83 C3 01 81 FB 00 01 00 00 7C B6 }
$f = {83 c4 0c 53 53 6a 03 53 6a 03 68 00 00 00 c0}
condition:
($a and $b) or $c or $d or ($openPhysicalDiskOverwriteWithZeros and $f)
}This YARA rule can be deployed in the following contexts:
This rule contains 7 string patterns in its detection logic.
Scenario: Legitimate scheduled job using schtasks.exe
Description: A legitimate system maintenance task scheduled via schtasks.exe may trigger the rule due to the use of command-line execution.
Filter/Exclusion: Check for schtasks.exe with CommandLine containing known legitimate job names (e.g., Cleanup, Backup, Update). Exclude tasks with User set to a service account or system context.
Scenario: Admin using PsExec for remote execution
Description: System administrators may use PsExec to remotely execute commands on managed systems, which could resemble the behavior of the BlackEnergy/Voodoo Bear implant.
Filter/Exclusion: Filter out events where PsExec is used with known admin credentials or against whitelisted hosts. Exclude processes initiated by domain admin accounts or with User field matching authorized admin users.
Scenario: PowerShell script execution for system monitoring
Description: A legitimate PowerShell script used for system monitoring or log analysis may trigger the rule due to the presence of suspicious command-line arguments or script execution patterns.
Filter/Exclusion: Exclude PowerShell scripts executed from known monitoring tools (e.g., PowerShell.exe with script paths in the C:\Windows\System32\WindowsPowerShell\v1.0\ directory). Filter based on script names or hash values of known monitoring scripts.
Scenario: Antivirus or endpoint protection tool execution
Description: Antivirus or endpoint protection tools may execute scripts or binaries that resemble malicious implants, leading to false positives.
Filter/Exclusion: Exclude processes associated with known security tools (e.g., Microsoft Defender, Bitdefender, Kaspersky). Use process names or parent process context to identify legitimate security tool activity.
**Scenario: System update or patching process using `