Çağrı Sevinç
Verified Expert in Engineering
Network Security Developer
Munich, Bavaria, Germany
Toptal member since June 9, 2025
Çağrı is a results-oriented, CISSP-certified cybersecurity analyst with a proven track record of enhancing organizational security. His expertise includes conducting comprehensive security audits, implementing proactive vulnerability management and mitigation strategies, handling incidents, and adjusting firewall rules for optimized threat detection. Çağrı is proficient in managing SIEM tools to ensure vigilant monitoring and spearheading the implementation of robust VPN solutions.
Portfolio
Experience
- Access Control - 10 years
- Cisco Routers - 10 years
- Firewalls - 10 years
- Log Analysis - 10 years
- IPsec - 5 years
- Ethical Hacking - 5 years
- Cybersecurity - 5 years
- Site-to-site VPN - 5 years
Preferred Environment
Windows, Teams
The most amazing...
...solution I've contributed to developing is an asset discovery tool within operational technology and industrial control systems.
Work Experience
Network Security Engineer
Turkey Air Traffic Control Center
- Built 58 site-to-site IPSEC VPN tunnels between the branch office's Cisco routers and the central FortiGate firewalls, analyzed debug logs for solving issues, and updated the configurations on both ends.
- Enabled SSL-VPN clients to connect remotely and adjusted FortiGate firewall objects and policies.
- Replaced the Cisco backbone routers with Palo Alto NGFW and configured them according to the proper rules.
- Enhanced log management capabilities and investigated offenses, events, and flows with IBM QRadar. Created related rules and checked daily alarms.
- Deployed a Claroty network visibility tool in the network and gained a holistic view of the network to detect anomalies, threats, and vulnerabilities depending on baseline security.
- Worked with the National Computer Incident Response Team (CIRT) to become more protected against adversaries through threat intelligence.
- Elevated system security by conducting thorough ISO 27001 audits and reporting the results to civil aviation and state authorities.
SOC Analyst
Siemens Energy
- Implemented log collector installations for powerplant components, optimizing data transmission to the AWS platform. Monitored and investigated daily alerts from remote facilities, conducting log and event analysis of multiple ICS components.
- Created security tickets and communicated findings to customers via Microsoft Teams calls or emails. Executed comprehensive log analysis using cutting-edge tools such as ELK (Elastic Stack).
- Established IPsec tunnels and remote desktop protocol (RDP) connections to address customer security issues swiftly.
- Strengthened the security posture by configuring ICS firewalls, ICS network components, and Scalence routers and switches, ensuring a multi-layered defense.
- Managed and deployed security configurations at Foreman, distributing to components with Puppet. Conducted thorough vulnerability assessments, leveraging Nessus for comprehensive insights.
- Optimized customers' Trend Micro and McAfee antivirus configurations to ensure they were up-to-date via the latest signature updates.
- Implemented application whitelisting via McAfee ePolicy Orchestrator (ePO) inside the customer network.
Network Engineer
Dhmi
- Deployed Cisco routers and switches for diverse aviation systems.
- Optimized IP connectivity between more than 50 radar and voice stations nationwide.
- Configured network technologies such as HSRP, Virtual Router Redundancy Protocol (VRRP), access lists, VLANs, and Spanning Tree Protocol (STP) on Cisco devices.
- Spearheaded comprehensive monitoring of LAN and WAN connections via SolarWinds and Cisco Prime.
- Analysed network issues and collected pcap files for further analysis.
- Worked in a day/night shift plan to ensure seamless network operations.
- Resolved one of the most significant network issues related to the operation of civil aviation. The backbone routers were going down repeatedly due to high CPU usage, causing all the flight data to get lost during air traffic management.
- Optimized Open Shortest Path First (OSPF) hello timers to a more convenient level to fix network issues.
Experience
Cisco Backbone Routers Replacement
In addition, I set up SSL-VPN clients for remote access. I implemented "monitor capture" on Cisco 4400 series routers to generate pcap files for troubleshooting and send them to an FTP server.
Education
Master's Degree in Cybersecurity
Middle East Technical University (METU) - Ankara, Turkey
Bachelor's Degree in Electronics and Communication Engineering
Suleyman Demirel University - Isparta, Turkey
Certifications
Certified Information Systems Security Professional (CISSP)
ISC2
IBM Certified SOC Analyst
IBM
Certified Incident Handler (E-CIH)
EC-Council
Blue Team Level 1 (BTL1)
Security Blue Team
IBM Certified Analyst – Security QRadar SIEM V7.5
IBM
Certified SOC Analyst
EC-Council
Splunk Core Certified Power User
Splunk
CompTIA Cybersecurity Analyst (CySA+)
CompTIA
ISO/IEC 27001:2022 Information Security Management Systems – Lead Auditor
Exemplar Global, Inc.
Fortinet Certified Associate in Cybersecurity
Fortinet
CrowdStrike Certified Falcon Administrator
CrowdStrike
Certified Ethical Hacker
EC-Council
AWS Certified Solutions Architect – Associate
Amazon Web Services
Skills
Tools
NMap, Nessus, VPN, IBM QRadar, ELK (Elastic Stack), McAfee ePolicy Orchestrator (ePO)
Paradigms
Cisco Certified Network Associate Routing & Switching
Industry Expertise
Cybersecurity
Platforms
Windows, Amazon Web Services (AWS)
Languages
Python
Other
Telecom Equipment & Solutions, Information Systems, Cisco, Cisco Routers, Firewalls, ASA Firewalls, Log Analysis, Event Analysis, HSRP, Virtual Router Redundancy Protocol (VRRP), Access Control, Open Shortest Path First (OSPF), Multiprotocol Label Switching (MPLS), EIGRP, Ethical Hacking, Cybersecurity Operations, Endpoint Detection and Response (EDR), IPsec, Site-to-site VPN, Network Engineering, CCNA, Teams, SIEM, Security Operations Centers (SOC), Palo Alto Networks, FortiGate, Tenable.OT, Incident Response, Splunk Enterprise Security
How to Work with Toptal
Toptal matches you directly with global industry experts from our network in hours—not weeks or months.
Share your needs
Choose your talent
Start your risk-free talent trial
Top talent is in high demand.
Start hiring