Ap0calypse

Hunt Hypothesis

This detection identifies potential early-stage malware activity or suspicious script execution patterns defined by the Ap0calypse YARA signature within Azure Sentinel workloads. Proactively hunting for this behavior allows the SOC team to validate the rule’s efficacy and uncover stealthy threats that may not yet trigger high-severity alerts, ensuring comprehensive coverage against evolving low-fidelity indicators.

YARA Rule

rule Ap0calypse: RAT
{
	meta:
		author = " Kevin Breen <[email protected]>"
		date = "2014/04"
		ref = "http://malwareconfig.com/stats/Ap0calypse"
		maltype = "Remote Access Trojan"
		filetype = "exe"

	strings:
		$a = "Ap0calypse"
		$b = "Sifre"
		$c = "MsgGoster"
		$d = "Baslik"
		$e = "Dosyalars"
		$f = "Injecsiyon"

	condition:
		all 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 6 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the Ap0calypse detection rule in an enterprise environment, including suggested filters and exclusions:

• Antivirus Real-Time Scanning on Large Archives

  • Scenario: The endpoint protection suite (e.g., CrowdStrike Falcon or Microsoft Defender) performs a scheduled deep scan of large .zip or .tar.gz archives containing legacy application binaries. During this process, the scanner extracts and analyzes thousands of files in rapid succession, mimicking the behavior of an active malware payload execution chain that triggers the Ap0calypse YARA rule.
  • Filter/Exclusion: Exclude processes where the parent process is the specific AV engine (e.g., csagent.exe, MsMpEng.exe) and the file extension matches known archive types (*.zip, *.tar.gz`). Additionally, filter out events occurring during the defined maintenance window (e.g., 02:00–04:00 UTC).

• Software Deployment via Configuration Management Tools

  • Scenario: An automated deployment job using Ansible or Chef pushes a new application update to a fleet of servers. The deployment agent extracts the software package, writes configuration files, and executes initialization scripts. This burst of file creation and script execution generates a high volume of process activity that matches the Ap0calypse signature for “suspicious script execution.”
  • Filter/Exclusion: Create an exclusion rule for processes spawned by known deployment agents (e.g., ansible-runner.exe, chef-client.exe) running on specific host groups labeled as “Deployment Targets.” Filter events where the file hash matches a known baseline of approved deployment artifacts.

• Database Backup and Maintenance Jobs

  • Scenario: A nightly SQL Server maintenance task executed by SQL Server Agent triggers a backup job that involves reading large data