Sakura Exploit Kit Detection

Hunt Hypothesis

The Sakura Exploit Kit may be used to deliver malicious payloads through compromised websites, indicating potential initial compromise. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage attacks before they escalate.

YARA Rule

rule sakura_jar : EK
{
meta:
   author = "Josh Berry"
   date = "2016-06-26"
   description = "Sakura Exploit Kit Detection"
   hash0 = "a566ba2e3f260c90e01366e8b0d724eb"
   sample_filetype = "unknown"
   yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
   $string0 = "Rotok.classPK"
   $string1 = "nnnolg"
   $string2 = "X$Z'\\4^=aEbIdUmiprsxt}v<" wide
   $string3 = "()Ljava/util/Set;"
   $string4 = "(Ljava/lang/String;)V"
   $string5 = "Ljava/lang/Exception;"
   $string6 = "oooy32"
   $string7 = "Too.java"
   $string8 = "bbfwkd"
   $string9 = "Ljava/lang/Process;"
   $string10 = "getParameter"
   $string11 = "length"
   $string12 = "Simio.java"
   $string13 = "Ljavax/swing/JList;"
   $string14 = "-(Ljava/lang/String;)Ljava/lang/StringBuilder;"
   $string15 = "Ljava/io/InputStream;"
   $string16 = "vfnnnrof.exnnnroe"
   $string17 = "Olsnnfw"
condition:
   17 of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 18 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Scheduled System Maintenance Task
  Description: A legitimate scheduled task runs a script that mimics exploit kit behavior, such as downloading a file or executing a command.
  Filter/Exclusion: Exclude tasks associated with Task Scheduler and containing maintenance, update, or backup in the task name.

• Scenario: Admin Performing Remote Code Execution (RCE) via PowerShell
  Description: An administrator uses PowerShell to execute a script remotely for system configuration or patching, which may trigger the same behavior as an exploit kit.
  Filter/Exclusion: Exclude PowerShell scripts executed from known admin tools like PowerShell.exe with runas or from IP addresses in the internal network range.

• Scenario: Software Update Deployment via SCCM
  Description: A Software Center or Configuration Manager (SCCM) update deployment downloads a file from a trusted internal server, which may be flagged by the detection rule.
  Filter/Exclusion: Exclude traffic from SCCM servers (SCCM or SMS) and files with known update hashes or file names.

• Scenario: Log Collection and Analysis Tool (e.g., Splunk, ELK) Processing Logs
  Description: A log processing tool temporarily executes a script or command to parse logs, which may resemble exploit kit activity.
  Filter/Exclusion: Exclude processes associated with Splunk, logstash, or kibana and filter by known log processing directories or file types.

• Scenario: Internal Penetration Test Using Mimikatz or Cobalt Strike
  Description: A red team or security team uses tools like Mimikatz or Cobalt Strike to simulate attack vectors, which may trigger the exploit kit detection.
  Filter/Exclusion: Exclude processes with Mimikatz, Cobalt Strike, or