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// File transfer & sharing

Port 990: ftp protocol, control, over TLS/SSL

Port 990 is assigned by IANA to ftps (ftp protocol, control, over TLS/SSL).

990

How ftps works

File transfer & sharing
client:9901/32/33/3ftps? client:9901/32/33/3ftps?

Files are sent over port 990 in pieces and reassembled on the other side. Everything is encrypted: someone on the path only sees unreadable bytes.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
EncryptedTLS or built-in crypto
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
File transfer & sharing
01 Security

Is port 990 dangerous?

We have no specific security note for port 990. Its risk depends on the program actually listening on it. General advice for file transfer & sharing services:

  • Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).
  • Disable anonymous access and restrict shares or exports to known hosts.
  • Never publish file sharing protocols to the Internet.
02 Registry

IANA registry entries for port 990

ServicePortTransportDescriptionReferenceUpdated
ftps 990 TCP, UDP ftp protocol, control, over TLS/SSL - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 990, and is it reachable?

Linux

sudo ss -ltnup 'sport = :990'      # process listening on 990
sudo lsof -nP -i :990

macOS

sudo lsof -nP -i :990

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 990 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 990
netstat -ano | findstr :990

From another machine

nmap -p 990 -sV <host>
sudo nmap -sU -p 990 <host>
nc -zv <host> 990

Block it in the firewall

sudo ufw deny 990/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 990" -Direction Inbound -LocalPort 990 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 990 used for?

Port 990 is assigned by IANA to ftps (ftp protocol, control, over TLS/SSL).

Is port 990 TCP or UDP?

Port 990 is registered for TCP and UDP.

Is it safe to open port 990?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).

How do I check if port 990 is open?

On Linux run "ss -ltnup 'sport = :990'", on macOS "lsof -nP -i :990", and on Windows "netstat -ano | findstr :990" to see the local process. From another machine, "nmap -p 990 <host>" shows whether it is reachable.

05 Related
:445 SMB tcp · udp · critical risk :21 FTP tcp · udp · sctp · high risk :139 NetBIOS Session tcp · udp · high risk :69 TFTP udp · tcp · high risk :2049 NFS tcp · udp · sctp · high risk :873 rsync tcp · udp · high risk :20 File Transfer [Default Data] tcp · udp · sctp :115 Simple File Transfer Protocol tcp · udp

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