Konstantinos Agritelis

Professional Profile

L3 technical escalation engineer with strong experience resolving complex and high-impact issues across security, networking, email infrastructure, advanced threat protection, authentication, virtualization, cloud and voice systems. Experienced in customer-facing technical escalation, lab reproduction, deep log analysis, packet inspection and automation tool development.

Work Experience

L3 Escalation Engineer

Aug 2019 – Current

Fortinet — Praha, Czechia

Functioned as the highest-level technical escalation point prior to R&D involvement, resolving the most complex and high-impact cases.
Performed technical analysis and resolution across FortiMail, FortiSandbox, FortiDeceptor, FortiNDR, FortiPhish, FortiCamera, FortiRecorder and FortiVoice.
Reproduced customer environments in lab setups to troubleshoot real-world scenarios.
Analyzed diagnostic data, logs, traces and packet captures.
Resolved email security issues involving mail delays, TLS encryption, DKIM, SPF, DMARC, DLP, IBE and SAML SSO integrations.
Worked with Microsoft Exchange, Office 365, Google Workspace and secure logging integrations.
Automated testing and workflows using Python, PowerShell, C# and .NET tools.
Delivered technical training and contributed to knowledge base and certification content improvements.

Network Support Analyst

Oct 2018 – Aug 2019

AT&T — Brno, Czechia

Performed end-to-end troubleshooting across OSI Layers 1 to 3 in high-pressure operational environments.
Led incident investigation, fault isolation, steady-state recovery and SLA-driven resolution.
Supported MPLS solutions, fiber, T1/E1, T3/E3, ATM/IMA, PPP multilinks, LAN, WAN, WLAN and VPN infrastructures.
Worked with Cisco routers, switches, wireless access points, controllers, ANIRA devices and 4G backup devices.
Troubleshot Frame Relay, ATM, Ethernet, STP, VLANs, trunking, eBGP, iBGP, OSPF and EIGRP.

IT Manager & Network System Administrator

Apr 2018 – Sep 2018

Skiathos Palace — Skiathos, Greece

Configured Ubiquiti EdgeRouter and ISP bridged routing environments.
Installed and maintained Cisco, Linksys and Ubiquiti switching and wireless infrastructure.
Configured multiple SSIDs and VLAN separation for secure and segmented wireless networks.
Maintained Windows-based file servers and supported the hotel's end-to-end IT operations.

Technical Skills

Email Security & Systems

FortiMail, email gateways, TLS, DKIM, SPF, DMARC, DLP, IBE, SAML SSO, Microsoft Exchange, Office 365, Google Workspace.

Network & Security

SSL, encryption technologies, security certificates, packet analysis, firewalls, LAN, WAN, WLAN, VPN, routing and switching.

Advanced Threat Protection

FortiSandbox, malware analysis, MITRE ATT&CK reporting, YARA rules, ICAP, JSON APIs, FortiAnalyzer, FortiSIEM, syslog, CEF.

Automation & Scripting

Python, PowerShell, C#, .NET, API automation, scripting for lab workflows, troubleshooting utilities and custom technical support tools.

Authentication & Access Control

LDAP, SAML, RADIUS, identity-based access, directory synchronization, authentication flows and group mapping.

Virtualization & Cloud

VMware, Hyper-V, Microsoft Azure, Amazon Web Services and lab-based environment replication.

FortiMail FortiSandbox Wireshark Python PowerShell C# / .NET SAML LDAP RADIUS Azure AWS Office 365

Education

MSc Information Security & Computer Forensics

University of East London
Oct 2017 – Sep 2018

Computer security, ethical hacking, web application attacks, reconnaissance, scanning, gaining access, security management, ISO 27001/27002, SOA, GAP analysis.

Final Grade: Merit | EQF Level 7

BSc (Hons) Computer & Networks

University of East London
Oct 2014 – Jun 2017

Software development, database design, web development, network design, simulation, information security, ISO standards and project management.

Final Grade: First-Class Honours | EQF Level 6

Languages

Greek

Mother tongue

English

C2

Czech

A2

French

A1

Interests

Automotive Enthusiast

Passionate about performance tuning and maintenance, including hands-on work with a Nissan 350Z and Mazda RX-7.

Sport Shooting

Former competitive shooter with multiple medals in Hellenic National Shooting Championships, with strong emphasis on precision, discipline and safety.

Aviation

Enthusiastic about flying and family trips in a Cessna 182P Skylane whenever time and weather permit.

Technical Learning

Strong interest in troubleshooting methodology, automation, systems reliability and continuous improvement.

L3 Escalation Engineer | Email Security | Advanced Threat Protection