Angler Exploit Kit Detection

Hunt Hypothesis

Angler Exploit Kit activity is detected through unusual network traffic patterns and suspicious file downloads indicative of exploit kit infrastructure. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential compromise early and prevent lateral movement within the network.

YARA Rule

rule angler_flash_uncompressed : EK
{
meta:
   author = "Josh Berry"
   date = "2016-06-26"
   description = "Angler Exploit Kit Detection"
   hash0 = "2543855d992b2f9a576f974c2630d851"
   sample_filetype = "unknown"
   yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
   $string0 = "DisplayObjectContainer"
   $string1 = "Xtime2"
   $string2 = "(HMRTQ"
   $string3 = "flash.events:EventDispatcher$flash.display:DisplayObjectContainer"
   $string4 = "_e_-___-__"
   $string5 = "ZviJbf"
   $string6 = "random-"
   $string7 = "_e_-_-_-_"
   $string8 = "_e_------"
   $string9 = "817677162"
   $string10 = "_e_-__-"
   $string11 = "-[vNnZZ"
   $string12 = "5:unpad: Invalid padding value. expected ["
   $string13 = "writeByte/"
   $string14 = "enumerateFonts"
   $string15 = "_e_---___"
   $string16 = "_e_-_-"
   $string17 = "f(fOJ4"
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 system maintenance task, such as a Windows Update or disk cleanup, may trigger the rule due to similar network behavior.
  Filter/Exclusion: process.name != "wuauclt.exe" OR process.name != "cleanmgr.exe"

• Scenario: Admin Performing Remote Desktop Session
  Description: An administrator using Remote Desktop Protocol (RDP) to access a server may trigger the rule if the session involves network activity resembling exploit kit traffic.
  Filter/Exclusion: process.name != "mstsc.exe" OR destination.ip != <internal_network_range>

• Scenario: Legitimate Software Update via SCCM
  Description: A Software Center or Configuration Manager (SCCM) update process may mimic exploit kit behavior during package delivery.
  Filter/Exclusion: process.name != "ccmexec.exe" OR process.name != "smsts.exe"

• Scenario: Internal Network Monitoring Tool Traffic
  Description: Tools like Wireshark or tcpdump used for internal network analysis may generate traffic that resembles exploit kit activity.
  Filter/Exclusion: process.name != "wireshark.exe" OR process.name != "tcpdump.exe"

• Scenario: Automated Log Collection via Splunk or ELK
  Description: Automated log collection tools such as Splunk or ELK Stack may trigger the rule due to outbound HTTP traffic.
  Filter/Exclusion: process.name != "splunkd.exe" OR process.name != "logstash.exe" OR destination.port != 80 AND destination.port != 443