Network Filtering Toolkit
Build DLP, VPN clients, parental controls, traffic shapers, ad blockers, spam filters and transparent proxies with NetFilter SDK and ProtocolFilters — high-performance packet and content filtering for Windows, Linux and macOS. Use it from C / C++ / .NET / Delphi.
NetFilter SDK for Windows
Transparent, proxy-less filtering of TCP/UDP at transport level. Compatible with antiviruses, firewalls and other network filters. Includes gateway (server-side) components.
ProtocolFilters
Classifies packets, detects high-level protocols and filters the classified objects. Works with NetFilter SDK API or any other packet source.
NetFilter SDK for Linux
Filter TCP connections, allow or block UDP datagrams in user-mode apps, redirect outgoing connections — including gateway mode on a router machine.
NetFilter SDK for macOS
Transport-level filtering of TCP/UDP with process and user context for all network activity. Works on Intel and ARM64, together with ProtocolFilters.
What you can build
- DLP solutions
- VPN solutions
- Parental control and content filtering
- Traffic monitors, shapers and analyzers
- Ad blocking and email spam filtering
- Redirecting TCP / UDP to a local or remote proxy
- Decoding and filtering TLS / SSL protected connections
- Parsing TLS, HTTP, HTTP/2, POP3, SMTP, IMAP, FTP, XMPP and more
Current versions
September 26, 2026
NetFilter SDK for Windows & macOS
version 1.7.8.2
Windows changelog
macOS changelog
September 26, 2026
ProtocolFilters
version 1.3.9.0
changelog
March 27, 2026
NetFilter SDK for Linux
version 1.0.4.0
changelog