This hypothesis targets the presence of the SimpleUPX Cryptor, a tool frequently used by adversaries to compress and obfuscate malicious payloads to evade static analysis and signature-based detection. Proactively hunting for this specific cryptor in Azure Sentinel allows the SOC to identify early-stage intrusion attempts or dropped binaries that may be leveraging multi-layer encryption to hide their true functionality before execution.
rule SimpleUPXCryptorv3042005multilayerencryptionMANtiCORE
{
meta:
author="malware-lu"
strings:
$a0 = { 60 B8 [3] 00 B9 18 00 00 00 80 34 08 ?? E2 FA 61 68 [3] 00 C3 }
$a1 = { 60 B8 [4] B9 18 00 00 00 80 34 08 ?? E2 FA 61 68 [4] C3 }
condition:
$a0 at pe.entry_point or $a1 at pe.entry_point
}This YARA rule can be deployed in the following contexts:
This rule contains 2 string patterns in its detection logic.
Scenario: A developer or DevOps engineer manually runs a custom Python or C# script that implements a multi-layer encryption routine (e.g., AES followed by ChaCha20) to encrypt sensitive configuration files or API keys before committing them to a private repository or uploading them to a secure vault.
python.exe, dotnet.exe, node.exe) when the parent process is an IDE (e.g., code.exe, idea64.exe, visualstudio.exe) or a terminal emulator (e.g., powershell.exe, cmd.exe, bash.exe) and the working directory is within a standard source control path (e.g., C:\Users\<User>\source\, /home/<User>/projects/).Scenario: An enterprise backup or data migration tool (such as Veeam, Commvault, or a custom PowerShell script) performs a “secure copy” operation where it encrypts data in memory using a multi-pass algorithm before writing to a secondary storage location or network share, triggering the YARA rule on the temporary encrypted buffer or output file.
VeeamBackup.exe, CommvaultAgent.exe, wbadmin.exe) or exclude file paths located in standard backup directories (e.g., C:\Backup\, \\<BackupServer>\BackupShare\, D:\Migrations\).Scenario: A security team executes a periodic “canary token” or honeypot validation job that intentionally creates small, encrypted files with complex encryption layers to test detection coverage and verify that the EDR is catching known patterns, often scheduled via Task Scheduler.