Port 3410: NetworkLens SSL Event — A Registered Port Best Known for a Trojan

What Port 3410 Is

Port 3410 sits in the registered port range (1024-49151). These ports are assigned by IANA for specific applications and services — they require an organization to formally claim them, but unlike well-known ports (0-1023), they don't require elevated privileges to open.

The official registration: NetworkLens SSL Event, filed in 2002. NetworkLens was a network monitoring and policy management product. The service that was supposed to use this port has long since faded from relevance. You are unlikely to encounter it.

What Actually Uses This Port

Port 3410 is most commonly documented in security literature as the default port for Optix Pro (also tracked as Backdoor.OptixPro), a remote access trojan that became notorious in the early 2000s. Optix Pro gives attackers full remote control over an infected machine: file access, keylogging, webcam access, process manipulation.

The trojan listens on port 3410 waiting for its operator to connect. It can be reconfigured to use other ports, but 3410 remains the default — which means security scanners and threat actors alike still probe it.

SANS Internet Storm Center logs ongoing scanning activity targeting port 3410. Most of it is reconnaissance: automated systems checking whether anything is listening.¹

What to Do If You See It Open

# macOS / Linux — show what process is listening on port 3410
sudo lsof -i :3410

# Linux alternative
sudo ss -tlnp sport = :3410

# Windows
netstat -ano | findstr :3410
# Then look up the PID in Task Manager

If you find something listening here that you didn't put there, treat it seriously. Run current antivirus scans. The legitimate service is rare enough that an unexpected listener is more likely malicious than benign.

Why Unassigned and Dormant Ports Matter

The registered port range contains thousands of ports like this one: officially claimed, rarely used, largely forgotten. They matter for a few reasons:

Attack surface awareness. Dormant official registrations provide cover. Malware authors sometimes deliberately choose registered ports to make traffic look more legitimate, or simply because the ports are empty and convenient.

Firewall defaults. Many organizations block only well-known ports by default. Registered ports in the 1024-49151 range often pass through corporate firewalls unchallenged — which is exactly why they're attractive to malware.

Port exhaustion isn't the problem. There are 65,535 ports. The challenge isn't running out — it's keeping track of what's actually running where, and why.