Detecting Fileless Attacks On Endpoints

Detecting Fileless Attacks On Endpoints

Overview

Cybersecurity skill for detecting fileless attacks on endpoints. Follows industry best practices and security standards.

When to Use

Trigger phrases:

• "detecting fileless attacks on endpoints"
• "Building detection rules for fileless malware that operates entirely in memory"
• "Hunting for PowerShell-based attacks, reflective DLL injection, and WMI abuse"
• "Configuring endpoint telemetry (Sysmon, AMSI, PowerShell logging) to capture fil"

Use this skill when:

• Building detection rules for fileless malware that operates entirely in memory
• Hunting for PowerShell-based attacks, reflective DLL injection, and WMI abuse
• Configuring endpoint telemetry (Sysmon, AMSI, PowerShell logging) to capture fileless indicators
• Investigating incidents where traditional AV found no malicious files

Do not use for detecting file-based malware or for malware reverse engineering.

When NOT to Use

• When you lack proper authorization for testing
• For production systems without change management
• When the task requires legal or compliance expertise beyond technical scope

Prerequisites

• Sysmon with process creation and WMI event logging enabled
• PowerShell Script Block Logging and Module Logging enabled
• AMSI (Antimalware Scan Interface) enabled for script content inspection
• EDR with behavioral detection capabilities (MDE, CrowdStrike, SentinelOne)

Workflow

# Example: IOC detection
import re

IOC_PATTERNS = {
    "ip": r"\b(?:\d{1,3}\.){3}\d{1,3}\b",
    "domain": r"\b[a-z0-9-]+\.[a-z]{2,}\b",
    "hash_md5": r"\b[a-f0-9]{32}\b",
    "hash_sha256": r"\b[a-f0-9]{64}\b",
}

def extract_iocs(text: str) -> dict:
    return {k: re.findall(v, text) for k, v in IOC_PATTERNS.items()}

1. Define Detection Scope — Identify the specific fileless attacks on endpoints techniques or indicators to hunt. Map to MITRE ATT&CK tactics/techniques where applicable.
2. Collect Baseline Data — Gather historical logs and establish normal behavior patterns for fileless attacks on endpoints.
3. Build Detection Queries — Write detection rules, Sigma rules, or SIEM queries targeting fileless attacks on endpoints indicators.
4. Execute Hunts — Run queries against the collected data, starting with broad filters and narrowing down.
5. Triage Results — Investigate alerts, filter false positives, and validate findings against known-good behavior.
6. Document Findings — Record confirmed detections, IOCs, and affected systems. Update detection rules based on findings.

Tools

• SIEM Platform — Central log aggregation and query execution
• Sigma Rules — Vendor-agnostic detection rule format
• MITRE ATT&CK Navigator — Technique mapping and coverage analysis

Process

1. Reconnaissance — Gather target information, identify attack surface, enumerate services
2. Analysis/Exploitation — Execute the technique, analyze results, document findings
3. Reporting — Document IOCs, write findings, provide remediation recommendations

Verification

• All fileless attacks on endpoints procedures executed completely and documented
• Findings validated against multiple data sources
• False positives identified and filtered
• Results documented with evidence and timestamps
• Recommendations provided with risk-based prioritization

Anti-Rationalization Table