Port 990 FTPS (implicit) · TCP

What runs on port 990

FTPS with implicit TLS: the TLS handshake happens before any FTP command, as with HTTPS. Explicit FTPS on port 21 (AUTH TLS) is the standardised form; implicit on 990 is older but still widely deployed by hosting panels and banks' file-exchange systems. Both still need a passive port range opened.

Software that uses it: vsftpd · ProFTPD · FileZilla Server · IIS FTP · Cerberus, Serv-U

Should port 990 be open?

Internet-facing only with authentication and care. It can be exposed when the service behind it is authenticated, rate-limited and kept up to date; most deployments are better off behind a VPN, an allow-list or a reverse proxy.

• Set pasv_min_port/pasv_max_port and open that range too, or transfers hang after login.

Check port 990

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :990'
sudo lsof -i :990

# from another machine: is it reachable?
nc -zv host 990
nmap -p 990 host
curl -v telnet://host:990      # raw TCP connect test, Ctrl-C to leave

A port that answers from the internet when it should not is the finding; nmap from a machine outside your network (or a VPS) is the honest test, because scans from inside the LAN pass the firewall you are trying to verify.

Allow or block port 990

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 990 proto tcp
sudo ufw deny 990/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 990 accept
nft add rule inet filter input tcp dport 990 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 990 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 990 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=990 protocol=tcp accept'

Replace 10.0.0.0/8 with the networks that need access. Allowing by source address is the rule that matters; "allow 990" with no source is just "open".

Related ports

• 21 FTP — FTP control; plaintext, replace with SFTP
• 22 SSH — SSH, SCP, SFTP, git over ssh
• 20 FTP data — FTP data channel (active mode)

Part of the port number reference. Ports are 16-bit numbers; see also the subnet calculator and the packet decoder, which shows ports inside TCP and UDP headers.

Questions