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Security Researcher & Network Engineer

Hello, I'm Md. Samsel Arifin Chowdhury

Six years of experience designing, securing, and automating enterprise network infrastructure — from FortiGate and BGP to self-built SOC platforms.

View Projects Experience Hire Me
6+
Years Exp
1200+
Cases Resolved
5
Certifications
samsel@security-lab:~$
$ show firewall policy status FortiGate 300E — Policy Active FortiGate 500E — IPSec Tunnel UP Sophos UTM — WAF Rules: 247   $ show bgp summary Neighbor: 10.0.0.1 — ESTABLISHED Prefixes: 142 / Up/Down: 2d 14h   $ verify nse4 certification [✓] NSE 4 — FortiOS 7.2 — Oct 2023 $
Introduction

Meet ARIFIN

A short introduction to my background, expertise, and the kind of work I love doing.

Video Introduction

Network Security Engineer
Based in Dhaka, Bangladesh

In this short video I walk through my background in enterprise network security, the tools I use daily, and how I approach complex infrastructure challenges — from FortiGate firewall migrations to ISP-level BGP routing.

FortiGate & Sophos Firewall Expert
BGP, OSPF, MPLS, EIGRP Routing
ISO/IEC 27001 ISMS Policy
1,200+ Technical Cases Resolved
CCNA + NSE4 + MCSA Certified
My Certifications Work History
StatusOpen to Opportunities
NSE 4Fortinet Certified
About Me

Md. Samsel Arifin Chowdhury

As a network and cybersecurity engineer with 6+ years of experience, I specialize in designing, securing, and optimizing complex IT infrastructures across enterprise environments, with expertise in network architecture (LAN/WAN), VPN technologies, and advanced security implementations including Fortinet FortiGate, Sophos UTM, and Palo Alto firewalls. I bring strong proficiency in routing and switching (Cisco, BGP, OSPF, MPLS) and system administration across Windows Server, Linux, and Unix platforms, while actively developing VPN protocol automation scripts (Singbox, Hysteria2) using Bash to support scalable infrastructure operations.

A core part of my recent work has been architecting SENTINEL, an internal security monitoring platform I built independently — featuring cross-platform agents, file-integrity monitoring, USB DLP, secret-egress detection, GitHub secret scanning, malware scanning, and real-time SOC alerting. I have also developed fleet-scale automation pipelines for DNS integrity monitoring, VPN egress validation, and leak/performance detection across globally distributed server infrastructure.

I lead ISO/IEC 27001 implementation and compliance maintenance, covering policy development, audit readiness, and security governance, alongside experience in data center networking, performance optimization, patch management, and proactive threat mitigation. Having resolved 1,200+ technical cases, I focus on improving system reliability, strengthening security posture, and driving operational efficiency through automation and best practices.

Emailsamselarifinchowdhury@gmail.com
LocationBanasree, Dhaka - 1219
Phone+8801521428553
EducationBSc CSE, BIST (CGPA 3.23)

Core Competencies

Firewall Config — FortiGate, Sophos, Cisco95%
Routing Protocols — BGP, OSPF, MPLS, EIGRP90%
VPN — IPSec, SSL, Site-to-Site92%
VLAN / STP / Layer 2-3 Architecture88%
ISMS / ISO 27001 / Security Policy80%
Security Automation & Scripting (Bash)90%
SIEM / SOC Monitoring (Wazuh)85%
My Projects Get In Touch
Career Journey

Work Experience

From network administration to enterprise security engineering — a 6-year progression through Bangladesh's leading technology firms.

Kolpolok Limited

Dhaka, Bangladesh
Current
Sr. IT Engineer March 2025 — Present
  • Manage global IT infrastructure across multiple regions, including enterprise VPN (AnyConnect, OpenVPN, WireGuard, Ocserv) and cloud-based systems
  • Lead IT modernization projects — network upgrades, system implementations, and security automation rollouts
  • Architected SENTINEL, a self-hosted endpoint security & DLP platform with FIM, USB DLP, secret-egress detection, and real-time SOC alerting
  • Built automation pipelines (Singbox + Hysteria2) that cut VPN deployment time and improved fleet reliability
  • Developed unattended monitoring pipelines for DNS integrity and fleet health, replacing manual daily checks
  • Deployed nightly VPN egress validation across the global server fleet — automated leak detection and performance grading
  • Implemented automated P2P/torrent detection and progressive enforcement on multi-tenant Ocserv infrastructure
  • Delivered DNS filtering & ad-blocking across 170+ servers in EU, USA, and Asia, reducing malicious traffic
  • Implemented firewall automation, IP attack detection, rate-limiting, and geo-blocking to mitigate real-time threats
  • Built Wazuh SIEM dashboards for endpoint visibility, alerting, and compliance monitoring
  • Led incident response for device compromise, infrastructure vulnerabilities, and service disruptions
  • Enforced ISO/IEC 27001 by implementing 30+ security policies and org-wide training
  • Performed internal audits and risk assessments to maintain continuous ISO 27001 compliance
  • Collaborated with auditors and consultants on ISO certification and surveillance audits
InfrastructureCloudIT LeadershipSecurity ComplianceTeam Management

BacBon Limited

Dhaka, Bangladesh
1 yr 4 mo
Network Security Engineer November 2023 — February 2025
  • Install, configure, and maintain server OS — Windows Server, Linux, Unix
  • Draft, review, and update ISMS policies aligned with ISO/IEC 27001 standards
  • Configure and manage FortiGate, Sophos, and Cisco firewalls and enterprise switches
  • Implement and maintain SSL VPN, IPSec tunnels, and certificate-based auth
  • Monitor SIEM tools (Splunk), respond to security alerts, and document incidents
  • Delivered end-to-end network and server infrastructure setup for the USAID Higher Secondary Education Activity (HSEA) project
FortiGateSophos UTMISO 27001IPSecSSL VPNSplunkLinux

Aamra Networks Limited

Dhaka, Bangladesh
11 mo
Network Engineer — Technical Support November 2022 — October 2023
  • Maintained enterprise LAN/WAN networks for ISP-level infrastructure
  • Configured advanced routing — OSPF, BGP, MPLS, EIGRP on Cisco routers
  • Managed Layer 2/Layer 3 — VLANs, STP, trunking, subnetting
  • High availability and redundant network architecture design
  • Resolved 1,200+ technical support cases across network and security domains
BGPOSPFMPLSEIGRPVLANISPHigh Availability

Business Network — Bnet

Dhaka, Bangladesh
11 mo
Executive Engineer, Network Administration June 2021 — May 2022
  • Administered enterprise routers, switches, and firewall configurations for business clients
  • Implemented VPN solutions and managed access control lists
  • Network performance monitoring, patch management, and incident response
  • Layer 2/Layer 3 topology management and troubleshooting
CiscoVPNACLNetwork AdminMonitoring

Virtually Testing Foundation

Remote / International
2 mo
Virtual Intern January 2021 — March 2021
  • Completed virtual internship focused on security testing fundamentals
  • Gained hands-on exposure to real-world security workflows and professional documentation
Security TestingInternship
Credentials

Certifications & Courses

Industry-recognized credentials in firewall engineering, network security, and system administration.

Portfolio

Security Projects

Real-world firewall deployments, ISP network configs, VPN setups, and homelab security builds.

My Products

Small Business Management App Bangladesh — Try Free 14 Days

If you run a shop in Bangladesh, you already have a system. It’s a khata under the counter, a calculator…

Expert Sep 2026
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Network Security

USAID’s Higher Secondary Education Activity — Network & Security Support Engineering

USAID’s Higher Secondary Education Activity, delivered through BacBon Limited — Keeping a donor-funded education program’s IT infrastructure secure, available, and…

education-sector firewall-management it-asset-management Mikrotik
Intermediate Jul 2026
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Security Automation

SENTINEL — Self-Hosted Endpoint Security & DLP Platform for Source-Code Protection

SENTINEL by Kolpolok — Watch, detect, and respond across every company device. One console for endpoint visibility, data-loss prevention, and…

cross-platform data-loss-prevention dlp edr
Expert Jul 2026
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Security Automation

IT Security Workflow Automation — Turning Manual Fleet Checks Into Unattended Reporting Pipelines

Automation as a Security Control — A family of unattended monitoring pipelines covering DNS resolution integrity, in-memory datastore health, and…

bash-automation dig dns-monitoring fleet-management
Advanced Jul 2026
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Security Automation

Automated VPN Egress Validation — Streaming Reachability, Leak Detection & Performance Grading at Fleet Scale

Continuous Control Validation for a Global VPN Fleet — Every server, every night: connect, verify no leak, measure performance, probe…

bash-automation control-validation dns-leak iptables
Expert Jul 2026
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Security Automation

Automated Torrent Detection & Progressive Enforcement on ocserv VPN Infrastructure

Acceptable-Use Enforcement at the Tunnel Layer — Real-time P2P detection on a multi-tenant ocserv fleet, with progressive enforcement: immediate egress…

acceptable-use-policy bash-automation conntrack infrastructure-automation
Advanced Jul 2026
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My Products

Hisabio – Smart Budget Planner & Monthly Budget Planner | Avail 14 Day Free Trial

Meet Hisabio — Smart Budget Planner That Keeps Your Money (and Your Sanity) Intact. Tired of wondering where your paycheck…

expense tracker app free budget planner income expense manager investment tracker
Advanced Jun 2026
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ISO 27001 & Compliance

ISO 27001:2022 ISMS Development and Implementation at BacBon Limited

Project Summary ISO 27001:2022 implementation was the core focus of my role in 2024, where I served as an ISMS…

annex-a audit bacbon compliance
Advanced Apr 2026
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Network Infrastructure

Server Room Setup Design with Maintaining Proper Security Measures

Server Room Setup Design & Deployment: Secure, Scalable for an Edu-Tech Company Project Overview Client BacBon Ltd (Edu-Tech Company) Location…

Cisco-switch data-center-design Dell-PowerEdge hot-aisle-cold-aisle
Intermediate Apr 2026
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Knowledge Base

Security Blog

Firewall configs, network writeups, lab builds, and field notes from enterprise security work.

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Get In Touch

Contact Me

Available for security consulting, network architecture projects, and full-time opportunities.

Let's Work Together

Whether you need a firewall migration, network security audit, or want to discuss a new role — I'm ready to talk.

Emailsamselarifinchowdhury@gmail.com
Phone+8801521428553
LocationBanasree, Dhaka - 1219, Bangladesh
LinkedInlinkedin.com/in/MdSamsel