0x88 Exploit Kit Detection

Hunt Hypothesis

The 0x88 Exploit Kit Detection identifies potential exploitation attempts by malicious actors leveraging compromised websites to deliver payloads, indicating possible 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 zerox88_js3
{
meta:
	author = "Josh Berry"
	date = "2016-06-26"
	description = "0x88 Exploit Kit Detection"
	hash0 = "9df0ac2fa92e602ec11bac53555e2d82"
	sample_filetype = "js-html"
	yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
	$string0 = " new ActiveXObject(szHTTP); "
	$string1 = " Csa2;"
	$string2 = "var ADO "
	$string3 = " new ActiveXObject(szOx88);"
	$string4 = " unescape("
	$string5 = "/test.exe"
	$string6 = " szEtYij;"
	$string7 = "var HTTP "
	$string8 = "%41%44%4F%44%42%2E"
	$string9 = "%4D%65%64%69%61"
	$string10 = "var szSRjq"
	$string11 = "%43%3A%5C%5C%50%72%6F%67%72%61%6D"
	$string12 = "var METHOD "
	$string13 = "ADO.Mode "
	$string14 = "%61%79%65%72"
	$string15 = "%2E%58%4D%4C%48%54%54%50"
	$string16 = " 7 - 6; HTTP.Open(METHOD, szURL, i-3); "
condition:
	16 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 17 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A system administrator is using Wireshark to analyze network traffic for troubleshooting purposes and captures a packet from a known 0x88 Exploit Kit domain.
  Filter/Exclusion: process.name != "wireshark" or check for process.user == "admin" and process.name == "wireshark" to differentiate from malicious activity.

• Scenario: A scheduled job runs a PowerShell script that downloads a legitimate software update from a domain that is flagged by the 0x88 Exploit Kit detection rule.
  Filter/Exclusion: process.name == "powershell.exe" and check for process.args containing update or patch keywords, or verify the domain against a known whitelist of update servers.

• Scenario: A system backup tool (e.g., Veeam Backup & Replication) temporarily connects to a server that is part of a 0x88 Exploit Kit infrastructure during a network scan.
  Filter/Exclusion: process.name == "veeam.exe" or check for process.parent.name == "task scheduler" to identify legitimate backup operations.

• Scenario: An IT security tool (e.g., CrowdStrike Falcon) is performing a signature update and connects to a 0x88 Exploit Kit domain as part of its update process.
  Filter/Exclusion: process.name == "falcon.exe" or check for process.args containing update or signature to identify legitimate security tool behavior.

• Scenario: A remote desktop session (e.g., Microsoft Remote Desktop) is initiated from a user’s machine, and the connection is routed through a network device that is flagged by the 0x88 Exploit Kit rule.
  Filter/Exclusion: `process.name == “mst