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Day 33 of 180 · 18% complete
⚠️ Authorised Engagements Only. AV evasion techniques may only be applied on systems you own or have explicit written authorisation to test, with AV bypass specifically listed in scope. Applying these techniques against unauthorised systems constitutes a criminal offence under computer misuse legislation regardless of the outcome. All exercises in this lesson target your own VM lab environment only.
AV Evasion Basics for 2026 :— Day 32 showed how to escalate privileges on a compromised Windows host. Day 33 addresses the problem that comes before privilege escalation in a real engagement: actually landing the payload without getting caught. Antivirus detection has evolved significantly since the simple signature-scanning era. Modern endpoints run layered defences — signature scanners, behaviour monitors, and EDR systems with kernel-level API hooks sending telemetry to cloud analytics. Understanding how each layer detects threats, and where each layer fails, is foundational knowledge for penetration testing teams assessing whether an organisation’s endpoint defences would stop a real attacker. This lesson builds that mental model from first principles.
🎯 What You’ll Master Today
How signature-based detection works and exactly which payload characteristics it matches against
How behaviour-based detection monitors runtime API calls and process relationships
Why in-memory execution evades file-based signature scanning
The fundamental difference between traditional AV and modern EDR capabilities
The conceptual framework for AV evasion — what Day 34 payload obfuscation builds on
⏱️ 45 min · 3 exercises · VM lab environment #### 📋 Prerequisites — Complete Before Day 33 - Day 30: Post-Exploitation and Persistence — the Meterpreter sessions and post-exploit tools from Day 30 are the payloads that Day 33’s evasion techniques protect - Day 32: Windows Privilege Escalation — PrivEsc runs after payload delivery; Day 33 covers getting through endpoint defences to reach the Day 32 stage ### 📋 AV Evasion Basics 2026 — Contents 1. The Endpoint Security Detection Stack 2. Signature-Based Detection — How It Works and Where It Fails 3. Behaviour-Based Detection — API Monitoring and Heuristics 4. In-Memory Execution — Why It Evades File-Based Scanning 5. Traditional AV vs Modern EDR — The Capability Gap 6. Core AV Evasion Concepts for Pentesters 7. The AV Evasion Testing Workflow ## The Endpoint Security Detection Stack Understanding AV evasion requires understanding what you’re evading. Modern endpoint security is not a single tool with a single detection mechanism — it is a layered stack with multiple independent detection approaches, each covering different aspects of malicious activity. An evasion technique that defeats one layer may still be caught by another. The penetration tester’s goal is not to find the one perfect technique, but to understand which layers are deployed, what each layer detects, and how to measure whether evasion has succeeded or failed in the specific target environment.
The typical enterprise endpoint in 2026 runs three to four overlapping detection layers: signature-based static analysis (scanning files before execution), behaviour-based dynamic analysis (monitoring what processes do at runtime), memory scanning (detecting injected code in running processes), and in some cases application control (allowlisting approved executables). Each layer has strengths and gaps. The gap between signature detection and behaviour detection is the space that basic AV evasion occupies. The gap between behaviour detection and memory scanning is where more advanced evasion sits.
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Endpoint Security Detection Stack — Layers and Gaps
Layer 1: Signature Scanning (file on disk)
Detects: known malware files · Misses: encoded/obfuscated/novel payloads · In-memory: not applicable
Layer 2: Behaviour Monitoring (runtime API calls)
Detects: suspicious API chains, process injection · Misses: legitimate API use, sleep/evasion · In-memory: partly detects
Layer 3: Memory Scanning (injected code detection)
Detects: shellcode in process memory, reflective DLL · Misses: well-obfuscated/encrypted in-memory code
Layer 4: EDR Cloud Analytics (telemetry correlation)
Detects: multi-step attack chains across time · Highest coverage · Requires significant sophistication to evade
📸 The endpoint security detection stack showing four detection layers and the types of activity each catches. Effective evasion requires defeating all active layers — a payload that evades file signature scanning (Layer 1) but triggers behaviour monitoring (Layer 2) is still caught. Understanding which layers are deployed in the target environment is the first step of any AV evasion assessment.
Signature-Based Detection — How It Works and Where It Fails
Signature-based detection is the oldest and most reliable form of AV detection for known threats. The AV vendor’s research team analyses malware samples, extracts identifying byte sequences or computes hashes of the full file or key sections, and adds these signatures to a database that ships to endpoint clients through definition updates. When the AV engine scans a file, it extracts the same byte patterns or computes the same hashes and compares against the signature database. A match triggers a detection and the file is quarantined or deleted.
The fundamental limitation of signature detection is that it only catches what the signature database contains — known threats. An attacker who creates a new variant of an existing tool by changing any part of the binary will produce different byte sequences and different hashes, defeating hash-based signatures. Even pattern-based signatures targeting specific byte sequences can be defeated by modifying the code around those sequences. This is why every major offensive security tool — Metasploit, Cobalt Strike, Mimikatz — is immediately detected by most AV products (their signatures are in every database), but a custom-compiled version of the same functionality may evade many products.
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