Angler Exploit Kit Detection

Hunt Hypothesis

The Angler Exploit Kit Detection identifies potential exploitation attempts by malicious actors leveraging outdated or vulnerable software to deliver payloads. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate early-stage compromise attempts that may evade traditional detection methods.

YARA Rule

rule angler_html : EK
{
meta:
   author = "Josh Berry"
   date = "2016-06-26"
   description = "Angler Exploit Kit Detection"
   hash0 = "afca949ab09c5583a2ea5b2006236666"
   sample_filetype = "js-html"
   yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
   $string0 = " A9 3E AF D5 9AQ FA 14 BC F2 A0H EA 7FfJ A58 A3 B1 BD 85 DB F3 B4 B6 FB B2 B4 14 82 19 88 28 D0 EA 2"
   $string1 = " 2BS 25 26p 20 3F 81 0E D3 9C 84 C7 EC C3 C41M C48 D3 B5N 09 C2z 98 7B 09. DF 05 5EQ DF A3 B6 EE D5 "
   $string2 = "9 A1Fg A8 837 9A A9 0A 1D 40b02 A5U6 22o 16 DC 5D F5 F5 FA BE FB EDX F0 87 DB C9 7B D6 AC F6D 10 1AJ"
   $string3 = "24 AA 17 FB B0 96d DBN 05 EE F6 0F 24 D4 D0 C0 E4 96 03 A3 03 20/ 04 40 DB 8F 7FI A6 DC F5 09 0FWV 1"
   $string4 = "Fq B3 94 E3 3E EFw E6 AA9 3A 5B 9E2 D2 EC AF6 10c 83 0F DF BB FBx AF B4 1BV 5C DD F8 9BR 97v D0U 9EG"
   $string5 = "29 9B 01E C85 86 B0 09 EC E07 AFCY 19 E5 11 1C 92 E2 DA A9 5D 19P 3A BF AB D6 B3 3FZ B4 92 FF E1 27 "
   $string6 = "B A9 88 B8 F0 EBLd 8E 08 18 11P EE BFk 15 5BM D6 B7 CEh AF 9C 8F 04 89 88 5E F6 ED 13 8EN1p 86Vk BC "
   $string7 = "w F4 C8 16pV 22 0A BB EB 83 7D BC 89 B6 E06 8B 2A DC E6 7D CE. 0Dh 18 0A8 5E 60 0C BF A4 00M 00 E3 3"
   $string8 = "B7 C6 E3 8E DC 3BR 60L 94h D8 AA7k5s 0D 7Fb 8B 80P E0 1BP EBT B5 03zE D0o 2A B97 18 F39 7C 94 99 11 "
   $string9 = "kY 24 8E 3E 94 84 D2 00 1EB 16 A4 9C 28 24 C1B BB 22 7D 97c F5 BA AD C4 5C 23 5D 3D 5C A7d5 0C F6 EA"
   $string10 = "08 01 3A 15 3B E0 1A E2 89 5B A2 F4 ED 87O F9l A99 124 27 BF BB A1c 2BW 12Z 07 AA D9 81 B7 A6-5 E2 E"
   $string11 = " 16 BF A7 0E 00 16 BB 8FB CBn FC D8 9C C7 EA AC C2q 85n A96I D1 9B FC8 BDl B8 3Ajf 7B ADH FD 20 88 F"
   $string12 = "  ML    "
   $string13 = " AEJ 3B C7 BFy EF F07X D3 A0 1E B4q C4 BE 3A 10 E7 A0 FE D1Jhp 89 A0sj 1CW 08 D5 F7 C8 C6 D5I 81 D2 "
   $string14 = "B 24 90 ED CEP C8 C9 9B E5 25 09 C6B- 2B 3B C7 28 C9 C62 EB D3 D5 ED DE A8 7F A9mNs 87 12 82 03 A2 8"
   $string15 = "A 3A A2L DFa 18 11P 00 7F1 BBbY FA 5E 04 C4 5D 89 F3S DAN B5 CAi 8D 0A AC A8 0A ABI E6 1E 89 BB 07 D"
   $string16 = "C B5 FD 0B F9 0Ch CE 01 14 8Dp AF 24 E0 E3 D90 DD FF B0 07 2Ad 0B 7D B0 B2 D8 BD E6 A7 CE E1 E4 3E5 "
   $string17 = "19 0C 85 14r/ 8C F3 84 2B 8C CF 90 93 E2 F6zo C3 D40 A6 94 01 02Q 21G AB B9 CDx 9D FB 21 2C 10 C3 3C"
   $string18 = "FAV D7y A0 C7Ld4 01 22 EE B0 1EY FAB BA E0 01 24 15g C5 DA6 19 EEsl BF C7O 9F 8B E8 AF 93 F52 00 06 "
condition:
   18 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 19 string patterns in its detection logic.

Source Rule

False Positive Guidance

Scenario: A system administrator is performing a scheduled system update using WSUS (Windows Server Update Services).
Filter/Exclusion: Exclude traffic related to wsus or update tasks with known WSUS server IP addresses or domain names.
Scenario: A developer is running a CI/CD pipeline (e.g., Jenkins, GitLab CI) that deploys code to a staging environment, which includes executing scripts that mimic exploit kit behavior.
Filter/Exclusion: Exclude traffic from known CI/CD agents or jobs with specific job names like ci-deploy or staging-deploy.
Scenario: A scheduled backup job (e.g., using Veeam or Backup Exec) is transferring large files across the network, which may trigger the exploit kit detection due to high data transfer rates.
Filter/Exclusion: Exclude traffic from backup services or jobs with known backup-related processes or file paths (e.g., backup, snapshot, vmbackup).
Scenario: An IT admin is using PowerShell remoting (e.g., Invoke-Command) to remotely manage servers, which may include script execution that resembles exploit kit behavior.
Filter/Exclusion: Exclude PowerShell remoting traffic from known admin accounts or IP ranges used for remote management (e.g., powershell, Invoke-Command, or PSRemoting).
Scenario: A log shipping or data replication task (e.g., using Logstash or Splunk) is transferring logs between systems, which may trigger the detection due to unusual network patterns.
Filter/Exclusion: Exclude traffic related to log shipping tools or known log transfer protocols (e.g., logstash, splunk, rsync, or syslog protocols).