Angler Exploit Kit Detection

Hunt Hypothesis

Angler Exploit Kit activity is detected through unusual network traffic patterns and suspicious file execution behavior indicative of exploit kit deployment. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential compromise from targeted exploit kit campaigns.

YARA Rule

rule angler_flash2 : EK
{
meta:
   author = "Josh Berry"
   date = "2016-06-26"
   description = "Angler Exploit Kit Detection"
   hash0 = "23812c5a1d33c9ce61b0882f860d79d6"
   sample_filetype = "unknown"
   yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
   $string0 = "4yOOUj"
   $string1 = "CSvI4e"
   $string2 = "'fwaEnkI"
   $string3 = "'y4m%X"
   $string4 = "eOc)a,"
   $string5 = "'0{Q5<"
   $string6 = "1BdX;P"
   $string7 = "D _J)C"
   $string8 = "-epZ.E"
   $string9 = "QpRkP."
   $string10 = "<o/]atel"
   $string11 = "@B.,X<"
   $string12 = "5r[c)U"
   $string13 = "52R7F'"
   $string14 = "NZ[FV'P"
condition:
   14 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 15 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 payload or modifying system settings.
  Filter/Exclusion: Exclude tasks associated with known system maintenance tools like Task Scheduler or Windows Update by checking the task name or execution path (e.g., C:\Windows\System32\).

• Scenario: Admin Performing Patch Management
  Description: An administrator uses a tool like WSUS or SCCM to deploy patches, which may involve downloading and executing payloads that resemble exploit kit activity.
  Filter/Exclusion: Exclude activities related to patch management by checking the process name (e.g., wsusutil.exe, ccmexec.exe) or the source IP address of the update server.

• Scenario: Internal Security Tool Simulating Exploits
  Description: A security team uses a tool like Metasploit or Burp Suite to simulate exploit kit behavior during penetration testing or vulnerability assessment.
  Filter/Exclusion: Exclude traffic from known security testing tools by checking the source IP (e.g., internal security team IP range) or the process name (e.g., msfconsole.exe, burpsuite.jar).

• Scenario: Automated Log Collection and Analysis
  Description: A log management tool like Splunk or ELK Stack may trigger the rule when parsing or processing log files that contain strings resembling exploit kit payloads.
  Filter/Exclusion: Exclude log processing activities by checking the process name (e.g., splunkd.exe, logstash.jar) or the file path (e.g., /var/log/, C:\Program Files\Splunk\).

• Scenario: User-Initiated Software Installation
  Description: A user downloads and