BRev Port 4444 — Metasploit / Meterpreter
Port 4444 is the default LPORT for Metasploit payloads. A reverse shell generated with default settings calls back to the attacker on 4444, and a bind shell listens on it — which makes this the one entry in the reference whose significance is not about what the service does but about what its presence implies.
Our dataset puts it plainly: if this is open and you did not open it, you are already compromised. That is the correct reading on a server. There is no legitimate daemon that claims 4444; a listener there on a production host means either a payload with default settings, or a penetration test somebody forgot to mention. Treat it as an incident until proven otherwise — identify the process, capture it before killing it, and check outbound connections as well as inbound.
Two honest caveats. Selenium Grid’s hub listens on 4444 by default, so a build machine or a QA container legitimately has it open, and various proxy and tooling images pick it too. And a real attacker changes the default — a compromise that avoided 4444 is the norm, not the exception. So an open 4444 is strong evidence and a closed one is no evidence at all.
Port 4444 at a glance
| Field | Value | Detail |
|---|---|---|
| Port | 4444 | Registered |
| Service | Metasploit / Meterpreter | The default listener of the Metasploit framework. (TCP) |
| Category | Dev & tooling | dev servers, build tools, admin consoles |
| Exposure | Never | Never expose to the internet |
Should port 4444 face the internet? If this is open and you did not open it, you are already compromised.
Bind it to localhost or a private network. Mass scanners find these within minutes of a host appearing online.
What commonly goes wrong
You found 4444 listening on a production host
Do not just kill it. Identify the process and its parent, note the binary path and the user, capture the current connection list, and preserve what you can — the process name and its parent chain are the fastest route to how it got there. Then isolate the host at the network rather than rebooting it, which destroys memory-resident evidence.
It is Selenium and you want to be sure
A Selenium hub answers HTTP on /status with JSON describing the grid, and the process is a Java runtime with selenium in the classpath. A Meterpreter listener answers nothing meaningful to a browser. Identify the binary path and its parent process before deciding — a Java runtime under your CI user is a very different finding from an unnamed binary under www-data.
Check port 4444 yourself
No browser can open a raw TCP socket, so no web page can honestly tell you whether this port is open on a remote host. These are the real commands, generated for port 4444 — swap example.com for the host you are actually testing.
What on this machine is holding port 4444?
sudo ss -tlnp | grep :4444Lists the listening socket and the PID/program holding it. Drop sudo and you get the socket but not the process name.
sudo lsof -i :4444The macOS answer to "address already in use". Kill it with `kill -9 <PID>` once you are sure what it is.
netstat -ano | findstr :4444The last column is the PID. Match it in Task Manager’s Details tab, or `taskkill /PID <pid> /F`.
Is port 4444 reachable on another host?
nc -vz example.com 4444"succeeded!" means the TCP handshake completed — the port is open. "Connection refused" is closed; a hang until timeout means filtered (a firewall dropped it silently).
nmap -Pn -p 4444 example.comThe only common tool that distinguishes open / closed / filtered. -Pn skips the ping sweep, so it still works against hosts that ignore ICMP.
Test-NetConnection example.com -Port 4444Read TcpTestSucceeded: True = open. It is built in — nothing to install.
telnet example.com 4444A blank screen or a banner means it connected. "Connection refused" means closed. Quit with Ctrl-] then `quit`.
curl -v --max-time 5 telnet://example.com:4444Handy when telnet is not installed: "Connected to …" proves the TCP handshake, without curl trying to speak HTTP.
No web page can tell you whether a port is open on a remote host
A browser cannot open a raw TCP socket — there is no API for it, by design. So a site that reports “port 3389 is OPEN on 203.0.113.10” is not checking from your browser; it is asking its own server to scan on your behalf. That works, but it means their server sees the host you asked about, scans from their address rather than yours, and answers a question about their network path, not yours.
We don't have a server here and won't pretend to. So this page does three honest things instead:
| Port | Proto | Service | What it is | Exposure | |
|---|---|---|---|---|---|
| 4444 | tcp | Metasploit / Meterpreter | The default listener of the Metasploit framework.If this is open and you did not open it, you are already compromised. | Never |
http://host:port/ and times it. A connection that is established proves a socket is open; an instant refusal usually means nothing is listening; anything else is honestly reported as “can't tell”. Each attempt gives up after 2.5s.nc -vz example.com 443
nmap -Pn -p 443 example.com
telnet example.com 443
curl -v --max-time 5 telnet://example.com:443
This page cannot answer that, and neither can any other page — from your browser. Opening a TCP connection to an arbitrary host and port is not something JavaScript is allowed to do. Every “open port checker” that gives you a green tick is running the scan on their server. Which is fine, as long as you know what you are agreeing to: they learn which host and port you were worried about, and the answer they give you is about the route from their data centre — not from the internet as your users see it.
What to do instead
Run the check from outside your own network. Copy an nmap or nc line from the card above and run it from a machine that is not behind the same router — a phone on mobile data with a terminal app, a cheap VPS, a colleague's laptop. Running it from inside the LAN tests the LAN, not the internet, and will happily say “open” while the world sees nothing.
Then check the thing that is actually blocking it, in this order: the service is bound to0.0.0.0 and not 127.0.0.1 · the host firewall (ufw, firewalld, Windows Defender Firewall) · the cloud security group or the router's port-forward rule · and finally your ISP, which commonly blocks 25, 80 and 445 on residential lines whatever you configure.
What a browser genuinely can verify
One thing: that an HTTPS service answers. If what you actually want to know is “is my site up and how fast is it”, the latency test measures real round trips to a CORS-open URL. If the name doesn't resolve, or resolves somewhere unexpected, that is a DNS problem, not a port problem — and it is the more common cause of “my port is closed” than an actual firewall.
An IP address finds the machine; a port picks which program on it gets the traffic. TCP sets up a connection first — a handshake, ordered delivery, retransmission — which is why the web, email and SSH use it. UDP just sends the packet with no handshake and no guarantee it arrives, which is why DNS, video calls and games use it: late data is worse than lost data.
That difference is why a UDP port is so much harder to test. TCP either completes a handshake or it doesn't, so a tool can tell you. A UDP service that has nothing to say to an unexpected packet stays silent — and silence looks identical to a firewall dropping it.
The three ranges
0–1023Assigned by IANA to core services. On Unix, binding one needs root (or CAP_NET_BIND_SERVICE).1024–49151Registered by vendors for their applications. Any user can bind these — which is why every dev server lives here.49152–65535Never assigned. The OS hands these out as the SOURCE port of your outgoing connections. (Linux actually uses 32768–60999 by default.)Closed is not the same as filtered
Closed means the host answered: the packet arrived, nothing is listening, and you got an immediate refusal (a TCP RST). Filtered means nothing answered at all — a firewall dropped your packet in silence, so you wait for a timeout and learn nothing. The difference matters: closed proves the host is reachable and the port is free; filtered tells you only that something between you and it is discarding traffic.nmap reports the two separately. A browser cannot distinguish them, which is why this page reports a timeout as “can't tell” rather than guessing.
The one habit worth keeping
Bind services to 127.0.0.1 instead of 0.0.0.0 unless something outside the machine genuinely needs them, and reach them over SSH or a VPN. Every database on the never-expose list above ships with that advice, and the leaks all begin the same way: a default bind address, a cloud instance with a public IP, and a scanner that found it within the hour.
The blocked-port list this page uses is the WHATWG Fetch Standard's “bad port” table — the ports every browser refuses to connect to (Chrome calls it ERR_UNSAFE_PORT). Local probing is additionally gated by Chrome's Local Network Access permission, which replaced Private Network Access and ships in Chrome 142.
FAQ
Is port 4444 dangerous?
The port itself is ordinary. What matters is that it is the default for Metasploit reverse shells, so an unexplained listener on a server is strong evidence of compromise and should be handled as an incident.
Can I just block port 4444?
It does very little. Attackers choose the port, and 443 or 53 are far more likely precisely because they pass through egress filters. Outbound filtering by policy and egress monitoring are the useful controls, not a rule for one number.
What legitimately uses 4444?
Selenium Grid’s hub is the common one, plus some proxy and testing tools. On a build or QA machine that is expected; on a database or web server it is not.