Build Your Own Burp Collaborator with Interactsh in 15 Minutes

What You'll Build

Burp Suite's Collaborator server is essential for detecting out-of-band interactions, but it requires Burp Pro. Interactsh is an open-source alternative that gives you the same capability: a server that logs DNS, HTTP, and SMTP requests, perfect for catching blind vulnerabilities.

Prerequisites

A Linux VPS with a public IP (DigitalOcean/Vultr $5/month droplet works)
A domain name with DNS access
Basic command line comfort
15 minutes

Step 1: Configure Your Domain's DNS

First, point your domain's DNS to your server. You need NS records for delegation.

In your domain registrar's DNS panel, add these records (replace 1.2.3.4 with your VPS IP):

code
Type: A
Name: ns1.interact.yourdomain.com
Value: 1.2.3.4

Type: A  
Name: ns2.interact.yourdomain.com
Value: 1.2.3.4

Type: NS
Name: interact.yourdomain.com
Value: ns1.interact.yourdomain.com

Type: NS
Name: interact.yourdomain.com  
Value: ns2.interact.yourdomain.com

This delegates all *.interact.yourdomain.com subdomains to your server.

Step 2: Install Interactsh Server

SSH into your VPS and install Go if needed:

bash
wget https://go.dev/dl/go1.21.5.linux-amd64.tar.gz
sudo tar -C /usr/local -xzf go1.21.5.linux-amd64.tar.gz
export PATH=$PATH:/usr/local/go/bin

Install Interactsh:

bash
go install -v github.com/projectdiscovery/interactsh/cmd/interactsh-server@latest
sudo mv ~/go/bin/interactsh-server /usr/local/bin/

Step 3: Generate SSL Certificate

Interactsh needs a wildcard certificate for HTTPS:

bash
sudo apt update && sudo apt install certbot -y
sudo certbot certonly --manual --preferred-challenges=dns \
  -d interact.yourdomain.com -d *.interact.yourdomain.com

Certbot will ask you to create a TXT record. Add it to your DNS:

code
Type: TXT
Name: _acme-challenge.interact.yourdomain.com
Value: <value-from-certbot>

Wait 2 minutes for DNS propagation, then press Enter in certbot.

Step 4: Launch the Server

Create a startup script:

bash
sudo nano /usr/local/bin/start-interactsh.sh

Add this content:

bash
#!/bin/bash
interactsh-server \
  -domain interact.yourdomain.com \
  -ip 1.2.3.4 \
  -cert /etc/letsencrypt/live/interact.yourdomain.com/fullchain.pem \
  -privkey /etc/letsencrypt/live/interact.yourdomain.com/privkey.pem \
  -listen-ip 0.0.0.0

Make it executable and run:

bash
sudo chmod +x /usr/local/bin/start-interactsh.sh
sudo /usr/local/bin/start-interactsh.sh

Step 5: Test Your Server

Generate a test payload:

bash
curl -X POST https://interact.yourdomain.com/register

You'll get a unique subdomain like c5q5m8g0kq8pxxxxxx.interact.yourdomain.com. Trigger it:

bash
curl http://c5q5m8g0kq8pxxxxxx.interact.yourdomain.com
ping c5q5m8g0kq8pxxxxxx.interact.yourdomain.com

Check for interactions:

bash
curl https://interact.yourdomain.com/poll?id=c5q5m8g0kq8pxxxxxx&secret=<secret-from-register>

You should see JSON with your HTTP and DNS requests logged!

Step 6: Use in Practice

Test SSRF in a vulnerable app:

bash
# In target application vulnerable to SSRF:
curl http://vulnerable-app.com/fetch?url=http://test.interact.yourdomain.com/ssrf-probe

For automated testing, integrate with tools:

bash
# With nuclei templates
nuclei -u https://target.com -interactsh-url https://interact.yourdomain.com

Make It Permanent

Create a systemd service:

bash
sudo nano /etc/systemd/system/interactsh.service

ini
[Unit]
Description=Interactsh Server
After=network.target

[Service]
Type=simple
User=root
ExecStart=/usr/local/bin/start-interactsh.sh
Restart=always

[Install]
WantedBy=multi-user.target

Enable it:

bash
sudo systemctl daemon-reload
sudo systemctl enable interactsh
sudo systemctl start interactsh

Where to Go Next

Set up the Interactsh web dashboard for a GUI
Configure email (SMTP) interaction logging
Integrate with your CI/CD pipeline for automated vulnerability scanning
Use Interactsh client CLI for easier payload generation
Explore advanced filtering rules in the server config

You now have a production-ready OOB interaction server that costs $5/month instead of $400/year for Burp Pro. Perfect for bug bounties, pentests, and red team engagements.