Harold
Eustaquio
Passionate full-stack developer and systems programmer with deep expertise across the entire technology stack — from low-level Rust systems to modern web applications. I build developer tools, open-source libraries, and security-focused software with a strong emphasis on performance and reliability.
Crafting Digital Experiences
From low-level systems to full-stack web — I work across the entire stack with passion and precision.
I'm Harold Eustaquio, a full-stack developer and systems programmer based in the Philippines. I go by surelle-ha online — a handle that's traveled with me across open-source projects and technical communities.
My journey started with web development but quickly expanded into systems programming when I discovered Rust. Today I bridge both worlds — building high-performance backend systems while crafting polished web interfaces with Vue / Nuxt and React / Next.js.
Security isn't an afterthought for me — it's a mindset. I actively study offensive security tools like Burp Suite, Metasploit, and Wireshark, and I've built security-focused applications that help developers find vulnerabilities before attackers do.
When I'm not coding, you'll find me distro-hopping across Linux environments, contributing to open-source projects, or exploring the Solana blockchain ecosystem.
Tools of the Trade
A curated collection of technologies I've mastered across the full development lifecycle.
🎨 Frontend 0
⚙️ Backend 0
🏗️ Frameworks 0
🗄️ Databases 0
🚀 DevOps 0
🔒 Security 0
🐧 Linux 0
⛓️ Blockchain 0
AI AI 0
> Always learning. Always building. _
What I've Built
A selection of projects that showcase my range — from systems-level Rust to full-stack web applications.
The Hacker's Toolkit
Security isn't just a feature — it's a discipline. From OSINT to exploitation, I work with the same tools security professionals use.
Security Tools
Open-source intelligence and forensics platform for link analysis and data mining.
Industry-leading web vulnerability scanner and intercepting proxy.
Network protocol analyzer for real-time packet capture and analysis.
Advanced penetration testing framework for developing and executing exploits.
Automated SQL injection and database takeover tool.
Linux Distributions
# Security mindset
const approach = {
offensive: "know your enemy",
defensive: "protect by design",
mindset: "assume breach",
}
Let's Build Something
Have a project in mind, or just want to connect? My inbox is always open.
Currently open to full-time roles, consulting, and interesting open-source collaborations. Response time is typically within 24 hours.