This detection rule identifies the execution of known WannaCryptor ransomware samples within the environment to confirm the presence of this specific threat family. Proactively hunting for these matches in Azure Sentinel is essential because early identification allows the SOC team to isolate affected assets before lateral movement occurs, even when initial alerts are flagged with low severity.
rule Wanna_Sample_84c82835a5d21bbcf75a61706d8ab549: Wanna_Sample_84c82835a5d21bbcf75a61706d8ab549
{
meta:
description = "Specific sample match for WannaCryptor"
MD5 = "84c82835a5d21bbcf75a61706d8ab549"
SHA1 = "5ff465afaabcbf0150d1a3ab2c2e74f3a4426467"
SHA256 = "ed01ebfbc9eb5bbea545af4d01bf5f1071661840480439c6e5babe8e080e41aa"
INFO = "Looks for 'taskdl' and 'taskse' at known offsets"
strings:
$taskdl = { 00 74 61 73 6b 64 6c }
$taskse = { 00 74 61 73 6b 73 65 }
condition:
$taskdl at 3419456 and $taskse at 3422953
}
This YARA rule can be deployed in the following contexts:
This rule contains 2 string patterns in its detection logic.
Here are 4 specific false positive scenarios for the WannaCryptor detection rule in an enterprise environment, along with suggested filters or exclusions:
Antivirus Endpoint Scanning of Legacy Archives
Process Name matches known AV scanner executables (e.g., MsMpEng.exe, csfalcon.exe) and the File Extension of the scanned object is .zip or .7z. Additionally, exclude events originating from specific “Archive Storage” file paths.Software Deployment via SCCM/Intune
C:\Windows\CCMCache). If the deployed software bundle includes a specific DLL or executable that shares a cryptographic hash or code signature with the WannaCryptor sample, the detection logic triggers immediately upon file extraction before the actual installation begins.Parent Process is ccmexec.exe (SCCM) or IntuneManagementExtension.exe, and the File Path contains keywords like \CCMCache\ or \Temp\. Alternatively, whitelist the specific SHA-256 hash of the known legitimate installer component.Backup Agent Snapshot Operations