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.