S.PEREIRO / LU --:--
ES EN
01 Sergio
02 Pereiro
03 Díaz
Check 4 Cyber Business Owner · Cybersecurity & Threat Detection Engineer
I've spent 23 years building and defending critical infrastructure. Detection engineering, SIEM, applied AI for defense. This is what I do — and where I invest my time.
23
years in IT / cybersecurity
8
years at the European Commission
5
personal AI projects
1
boutique consultancy
[01]

About me

// who · what · why

I'm an IT and cybersecurity professional with over 20 years of experience. I started as a systems administrator in 2002 and made the full jump to cybersecurity in 2012. Since then, I've built defensive infrastructure at scale — including 8 years supporting the European Commission — focused on threat detection engineering, SIEM and Splunk.

In 2018 I founded Check4Cyber, my own boutique consultancy in Luxembourg. From there I deliver detection engineering, audits and cloud migration to organizations that need more depth than an off-the-shelf service.

Over the last few years, AI has become my technical obsession. Not a formal job — it's the tool I use to build LUCRITAS, LiquiWatch, SIMB and AETHERIA. Neural reasoning, automation, LLM-assisted engineering. I believe the future of digital defense flows through here.

Based
Luxembourg / A Coruña
DOB
30 Jul 1981
Languages
ES · GL · EN · DE · FR
Stack
Splunk · Suricata · Arkime · AWS · Azure
[02]

Track record

// 23 years of operations · log -n 9
2022 — Present
DevSecOps Threat Detection Developer
European Commission — DIGIT S2 · Brussels
  • Threat detection development within the OpenTIDE framework.
  • Operating Stamus Networks IDS and Arkime as the FPC solution.
  • Splunk rules and automation; web & cloud security (Azure / AWS).
2018 — Present
Founder / Cybersecurity Consultant
Check 4 Cyber Sàrl-S — Luxembourg
  • Boutique cybersecurity consultancy for SMEs and large accounts.
  • Services: detection engineering, web audits, cloud migrations.
2012 — Jan 2026
CTO / Co-founder
ECHA UN OJO S.L. — Madrid · 13 yrs 6 mos
  • Co-founder and partner responsible for cybersecurity & systems consulting.
  • Web audits, cloud migrations and compliance.
  • Clients: Johnson & Johnson, Grupo Sanyres, Perfumes Club.
  • Business development & communication. Closed in January 2026.
2017 — 2021
Security SOC Analyst
European Commission — Brussels
  • Cisco Firepower NIDS and Snort rule tuning.
  • Incident response with Arcsight ESM / Logger.
  • Splunk PoC evaluation and integration.
2015 — 2017
CERT Supervisor
Mapfre S.A. — Madrid · 3 global DCs
  • Supervised the Mapfre CERT — incident response & threat hunting.
  • McAfee ESM coordination, pentesting support.
  • ISO 27001 / 9001 / PCI-DSS compliance.
2012 — 2015
Security Analyst
Mapfre S.A. — Madrid
  • SIEM operations and incident response in the CERT team.
  • Detections for Checkpoint, Snort, Apache, IIS, Splunk.
  • WAF, IDS and firewall rule implementation.
2007 — 2012
Systems Administrator
Allegro Systems International — Spain
  • Active Directory, DNS, DHCP, mail, VMware, Oracle, SQL Server.
  • Internal security via McAfee ePolicy Orchestrator and ISA Server.
2007
Systems Operator
Acens Technologies S.A. — Spain
  • Windows/Linux admin, backups and firewall rules.
2000 — 2007
Systems Administrator
Iberia Gestión Inmobiliaria S.L. — Spain
  • First chapter — systems and invoicing support.
[03]

Check 4 Cyber

// boutique cybersecurity consultancy · LU
The operating engine
CHECK 4 CYBER SARL-S
29 Boulevard Grande Duchesse Charlotte, L-1331 Luxembourg
CIF LU-31485966 · check4cyber.com ↗

Boutique cybersecurity consultancy founded in 2018 in Luxembourg. Design and operation of defensive capabilities for SMEs and large organisations that need more technical depth than a packaged service.

01 Detection Engineering
Splunk/Suricata rules, SIEM use cases, threat hunting.
02 Web App Security
OWASP audits, WAFs, hardening.
03 Cloud Security
AWS / Azure: defensive architecture, IAM, compliance.
04 Compliance
ISO 27001 · ISO 9001 · PCI-DSS, CISO support.
[04]

NO PASE

// network oriented public attack surface explorer
C4C product · in production
In production · nopase.com

NO PASE is Check4Cyber's SaaS product. A Network Oriented Public Attack Surface Explorer: it maps what your organisation exposes to the internet, captures it as an immutable snapshot, and tells you in plain language what changed and what to do about it.

  • > Continuous public attack surface mapping.
  • > Differential monitoring: every snapshot compared to the previous.
  • > Alerts by severity, confidence and business impact.
  • > Free scan without a card; continuous monitoring plans.
DOMAINS
nopase.com TLD
nopase.es TLD
nopase.eu TLD
nopase.org TLD
[05]

TOKENGOD

// crypto · participation engine
Crypto initiative
Fundraising · open to partners

Tokenization and digital asset participation project. Currently fundraising, with web2 and web3 domains already secured (including .eth). Open to strategic partners and community builders.

  • > Tokenized participation model.
  • > Reserved domains across web2 + ENS.
  • > Defined roadmap, looking for crypto partners.
  • > Synergy with the C4C defensive stack.
DOMAINS
tokengód.com TLD
tokengod.eu TLD
tokengod.es TLD
tokengod.eth ENS
[06]

End session

// channels open

If you work in cybersecurity, crypto or applied AI and think we could build something together — write.

$ echo "open for ops" | mail -s "hello" spereiro@c4c.lu
vCard · scan or download VCARD/3.0
NAME Sergio Pereiro Díaz
ORG Check 4 Cyber Sàrl-S
MAIL spereiro@c4c.lu
LU ✆ +352 691 350 470
ES ✆ +34 693 30 41 77
SAVE .VCF