Start detecting it today — not by port, but by behavior. Your network visibility will thank you. Drop a comment or ping me directly — I’m happy to share the rule templates.
Why standard file transfer monitoring fails, and the three telltale signs of FileCatalyst in flight FileCatalyst isn’t your average file transfer protocol. Built for high-speed, long-distance, and high-latency links, it’s a favorite in media, defense, and energy sectors. But that same efficiency makes it a blind spot for many security and network teams. filecatalyst detection
You can’t secure what you can’t see. So how do you detect FileCatalyst on your network — without false positives or drowning in packet captures? Start detecting it today — not by port, but by behavior
Let’s move past the blinking lights on the server and talk about real detection. Most people think: FileCatalyst uses port 33000 or 33001 (TCP/UDP) — case closed. Wrong. Why standard file transfer monitoring fails, and the
On the wire: TCP segments with payload size 24 or 32 bytes, repeating with millisecond precision. Normal background noise doesn’t do that. | Layer | Tool | What to look for | |-------|------|------------------| | Flow | ntopng, ElastiFlow | Asymmetric byte ratio >100:1 + constant packet gap | | Packet | tshark | tcp.payload_length == 24 and frame.time_delta between 5–15 sec | | IDS | Suricata | Custom rule matching TLS JA3S hash (ask me for the hash list) | | Logs | Zeek | ssl log with server_name containing unusual subdomains + cipher suite 0x1301 | Pro tip: FileCatalyst often coexists with Aspera or Signiant in media networks. Don’t confuse the two — Aspera uses FASP‑UDP with a different initial window and congestion signature. 4. Two Real‑World Detection Scenarios Scenario 1 – Unauthorized server in R&D Your NDR platform alerts on a workstation sending 800 Mbps to an unknown cloud IP on UDP/443. Standard inspection shows “QUIC” — but the packet size distribution doesn’t match QUIC. You pull a PCAP and see the 24‑byte control probe. It’s FileCatalyst Direct tunneling over port 443.
Beyond the Blink: How to Detect FileCatalyst Traffic on Your Network
A backup server initiates an outbound TCP connection to a partner IP on port 8080. The connection stays alive for 14 hours but only transfers data in three short bursts. That’s the FileCatalyst “hot folder” pattern — idle control channel, then scheduled bursts. 5. Don’t Forget The Blind Spot: UDP‑only mode In some high‑performance setups, FileCatalyst runs without TCP at all — no handshake, no keep‑alive, pure UDP data + UDP control. Most security tools assume a TCP control channel and will miss this entirely.