The presence of the s7hkimdb.dll file may indicate the presence of a Stuxnet variant, which is known for targeting industrial control systems. SOC teams should proactively hunt for this file in Azure Sentinel to identify potential advanced persistent threats and mitigate risks to critical infrastructure.
YARA Rule
rule Stuxnet_s7hkimdb
{
meta:
description = "Stuxnet Sample - file s7hkimdb.dll"
author = "Florian Roth"
reference = "Internal Research"
date = "2016-07-09"
hash1 = "4071ec265a44d1f0d42ff92b2fa0b30aafa7f6bb2160ed1d0d5372d70ac654bd"
strings:
$x1 = "S7HKIMDX.DLL" fullword wide
/* Opcodes by Binar.ly */
// 0x10001778 8b 45 08 mov eax, dword ptr [ebp + 8]
// 0x1000177b 35 dd 79 19 ae xor eax, 0xae1979dd
// 0x10001780 33 c9 xor ecx, ecx
// 0x10001782 8b 55 08 mov edx, dword ptr [ebp + 8]
// 0x10001785 89 02 mov dword ptr [edx], eax
// 0x10001787 89 ?? ?? mov dword ptr [edx + 4], ecx
$op1 = { 8b 45 08 35 dd 79 19 ae 33 c9 8b 55 08 89 02 89 }
// 0x10002045 74 36 je 0x1000207d
// 0x10002047 8b 7f 08 mov edi, dword ptr [edi + 8]
// 0x1000204a 83 ff 00 cmp edi, 0
// 0x1000204d 74 2e je 0x1000207d
// 0x1000204f 0f b7 1f movzx ebx, word ptr [edi]
// 0x10002052 8b 7f 04 mov edi, dword ptr [edi + 4]
$op2 = { 74 36 8b 7f 08 83 ff 00 74 2e 0f b7 1f 8b 7f 04 }
// 0x100020cf 74 70 je 0x10002141
// 0x100020d1 81 78 05 8d 54 24 04 cmp dword ptr [eax + 5], 0x424548d
// 0x100020d8 75 1b jne 0x100020f5
// 0x100020da 81 78 08 04 cd ?? ?? cmp dword ptr [eax + 8], 0xc22ecd04
$op3 = { 74 70 81 78 05 8d 54 24 04 75 1b 81 78 08 04 cd }
condition:
( uint16(0) == 0x5a4d and filesize < 40KB and $x1 and all of ($op*) )
}This YARA rule can be deployed in the following contexts:
This rule contains 4 string patterns in its detection logic.
Scenario: Scheduled System Maintenance Task
Description: A legitimate system maintenance task, such as Windows Update or disk cleanup, may involve the execution of a file named s7hkimdb.dll as part of a scheduled job.
Filter/Exclusion: Exclude files executed by scheduled tasks with known legitimate names (e.g., schtasks.exe, wuauclt.exe) or filter by process parent process such as taskhost.exe.
Scenario: Antivirus or Endpoint Protection Scan
Description: During a full system scan, an antivirus or endpoint protection tool may temporarily execute or access the s7hkimdb.dll file as part of its scanning process.
Filter/Exclusion: Exclude files accessed by known security tools (e.g., mpcmdrun.exe, mcafee.exe, avgnt.exe) or filter by process name associated with security software.
Scenario: Microsoft Windows System File
Description: The s7hkimdb.dll file may be a legitimate system file used by Windows or a Microsoft application, such as SQL Server or IIS, which could be accessed during normal operations.
Filter/Exclusion: Exclude files located in known system directories (e.g., C:\Windows\System32, C:\Windows\SysWOW64) or filter by file hash against a trusted database of known good files.
Scenario: Software Deployment via Group Policy
Description: A group policy update or software deployment may involve the s7hkimdb.dll file being deployed or executed as part of a legitimate enterprise software installation.
Filter/Exclusion: Exclude files executed by gpupdate.exe or msiexec.exe, or filter by the presence of a known enterprise deployment tool (e.g., SCCM, Microsoft Endpoint Manager).
**Scenario: Database Backup