Common attacks and weaknesses
- Brute force against the sa account.
- xp_cmdshell abused for command execution and ransomware deployment.
- Unencrypted logins on older configurations.
Port 1433: Microsoft SQL Server
Microsoft SQL Server database engine.
1433
How Microsoft SQL Server works
Databases & cachesThe application sends a SQL query to the Microsoft SQL Server server on port 1433, which returns rows from its tables. Encryption is optional: traffic is only protected if TLS is enabled on the server and the client.
- Transport
- TCP · UDP
- Exposure risk
- 8/10 high if reachable from the Internet
- Encryption
- Optional TLSTLS only if negotiated
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- Databases & caches
Is port 1433 dangerous?
How to secure it
- Never expose it to the Internet; use a VPN or private endpoints.
- Disable the sa account and xp_cmdshell.
- Force encryption and use Windows authentication.
IANA registry entries for port 1433
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| ms-sql-s | 1433 | TCP, UDP | Microsoft-SQL-Server | - | - |
// source: IANA service name and port number registry
Which program uses port 1433, and is it reachable?
Linux
sudo ss -ltnup 'sport = :1433' # process listening on 1433
sudo lsof -nP -i :1433macOS
sudo lsof -nP -i :1433
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1433 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 1433 netstat -ano | findstr :1433
From another machine
nmap -p 1433 -sV <host> sudo nmap -sU -p 1433 <host> nc -zv <host> 1433
Block it in the firewall
sudo ufw deny 1433/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 1433" -Direction Inbound -LocalPort 1433 -Protocol TCP -Action Block # Windows
What is port 1433 used for?
Microsoft SQL Server database engine.
Is port 1433 TCP or UDP?
Port 1433 is registered for TCP and UDP. In practice the service mostly uses TCP.
Is it safe to open port 1433?
It is rated 8/10 (high) when exposed to the Internet. Brute force against the sa account. Never expose it to the Internet; use a VPN or private endpoints.
How do I check if port 1433 is open?
On Linux run "ss -ltnup 'sport = :1433'", on macOS "lsof -nP -i :1433", and on Windows "netstat -ano | findstr :1433" to see the local process. From another machine, "nmap -p 1433 <host>" shows whether it is reachable.
Other databases & caches ports
:3306 MySQL / MariaDB tcp · udp · high risk :5432 PostgreSQL tcp · udp · high risk :6379 Redis tcp · critical risk :27017 MongoDB tcp · critical risk :9200 Elasticsearch tcp · udp · critical risk :1521 Oracle Database tcp · udp · high risk :11211 Memcached tcp · udp · high risk :5984 CouchDB tcp · udp · high risk