Open source firewall, runs on-premise
Network and Server Security: smart firewall, VPN and server hardening
We deploy an AI-assisted firewall built on OPNsense/pfSense, an end-to-end encrypted VPN and Linux/Windows server hardening with an open source stack, on your organization's own infrastructure. No expensive licences; your logs and traffic never leave your organization.
What is network and server security?
Network and server security means protecting your organization's network traffic, remote access and servers against unauthorised access and attack, in layers. The firewall filters traffic, the VPN encrypts remote access, and server hardening shrinks the attack surface of your systems. For most organizations the critical question is not the tool itself but where traffic and logs are processed. Sending security data to external cloud services is not the preferred option for most public institutions and SMEs.
C3T is not a product reseller; we are the team that implements and operates. We deploy the open source stack on your own infrastructure, configure it for your organization and, on request, take on operational responsibility.
How is open source network security set up?
C3T builds a secure network on an AI-assisted firewall based on OPNsense or pfSense, an end-to-end encrypted VPN using WireGuard/OpenVPN, and Linux/Windows server hardening. The entire stack runs on-premise, on your organization's own infrastructure; traffic and logs never leave. The network is segmented, the firewall is configured with rules specific to your organization, anomalous behaviour is flagged by on-premise AI, servers are hardened with secure configuration, and logs are kept under Law No. 5651. The result is enterprise-grade security without expensive commercial licences, meeting the requirements of Law No. 5651, BİGR (Turkey's Information and Communication Security Guide) and ISO 27001 A.13.
What we do
We deliver network and server security along four axes: secure network architecture, smart firewall, end-to-end encrypted VPN and server hardening. All of it runs on-premise and is fully auditable.
Secure network architecture
We design the network from the ground up with segmentation and layered defence, and secure your existing network.
- Network segmentation and VLAN separation
- DMZ and defence layers
- Traffic flow control
- Secure reconfiguration of existing infrastructure
Smart firewall (OPNsense / pfSense)
We deploy an open source firewall with AI-assisted threat blocking.
- Rule sets tailored to your organization
- AI-assisted anomaly detection
- Dynamic threat blocking
- IDS/IPS integration
End-to-end encrypted VPN
We connect remote workers and branch offices over encrypted, authenticated tunnels.
- WireGuard / OpenVPN deployment
- Remote worker and branch access
- Per-user and per-device permissions
- Infrastructure hosted on your own server
Server hardening
We harden Linux and Windows servers using secure configuration principles.
- Disabling unnecessary services and ports
- Patch and update management
- AI-assisted behavioural analysis
- Auditable configuration report
The open source stack we use
Instead of commercial licences we deploy mature open source tools, and run all of them on-premise on your organization's own infrastructure.
OPNsense / pfSense
Mature open source firewall platforms with no commercial licence required; we configure and operate them specifically for your organization.
WireGuard / OpenVPN
End-to-end encrypted, authenticated VPN tunnels; the infrastructure is hosted on your own server.
On-premise AI
Traffic and behavioural analysis is performed by models running inside your organization; threats are detected without network data ever leaving.
Which compliance obligations does it meet?
We build the secure network and server architecture to meet your organization's legal and administrative obligations.
Law No. 5651 (logging)
We configure network traffic and access logs to be kept with timestamps and integrity protection, stored inside your organization.
BİGR — network security
We implement the network security and access control measures of BİGR (Turkey's Information and Communication Security Guide) with open source tools, on-premise.
ISO 27001 A.13
We build the architecture to satisfy the communications security controls (network controls, network services and information transfer security).
Why C3T
We implement, deploy and operate — and take responsibility
C3T does not write a consultancy report and walk away. We bring the secure network architecture to life, configure the open source firewall and VPN for your organization, harden Linux and Windows servers and, on request, take on ongoing operational responsibility. The entire stack runs on-premise, on your organization's own infrastructure; your traffic and logs never leave. The result is enterprise-grade security that preserves data sovereignty, without being tied to expensive commercial licences.
Frequently asked questions
How do you choose between pfSense and OPNsense?
Both are mature, open source firewall platforms. We select, configure and operate the one that fits your hardware, existing network topology and management preferences. There is no commercial licence cost; we write the rule set specifically for your organization and update it over time as needs change.
Can you connect remote workers securely over VPN?
Yes. We deploy end-to-end encrypted, authenticated remote access with WireGuard or OpenVPN, and restrict access on a per-user and per-device basis. The VPN infrastructure runs on your own server and does not depend on a third-party cloud.
What does server hardening cover?
On Linux (Ubuntu/CentOS) and Windows Server it covers disabling unnecessary services, secure configuration, regular patch management, access restriction and AI-assisted behavioural analysis. Every step is reported in an auditable form.
Do you meet the Law No. 5651 log retention obligation?
Yes. We configure network traffic and access logs to be kept with timestamps and integrity protection, as required under Law No. 5651. Logs are stored on your own infrastructure; exporting them elsewhere is not required.
What does an AI-assisted firewall mean?
It analyses firewall traffic with models running on-premise, flags unusual behaviour and generates dynamic rules based on threat intelligence. Analysis takes place inside your organization; traffic data never leaves. The aim is to respond quickly to evolving threats, on top of static rules.
Do you implement it, or only deliver a report?
We implement, deploy and operate. C3T does not write a consultancy report and walk away; we bring the secure network architecture to life, configure the firewall and VPN, harden the servers and, on request, take on ongoing operational responsibility.
How secure are your network and servers?
Let's assess your current network topology and your firewall and VPN needs together. In a free feasibility call we'll clarify what can be done with an open source stack, without your traffic ever leaving your organization.