ZipLink Internet Blocked Ports
Blocked Ports
An internet port is an additional piece of information that helps identify a process or service. For example, web browsing is associated with port number 80. The Internet Assigned Numbers Authority maintains the Service Name and Transport Protocol Port Number Registry and defines legitimate service names and port numbers.
To protect the privacy and security of its network and its customers, ZipLink Internet blocks internet ports that are vulnerable to exploitation by malicious software (viruses, botnets, worms, distributed denial of service attacks, SPAM and others) and can harm our network as well as our customers. Below is a list of ports that ZipLink Internet blocks and why.
Port 0
Reserved
This port is reserved. No genuine internet traffic will use this port. Common exploits and vulnerabilities leverage this port.
Port 17 (qotd)
Quote of the Day
This port is routinely exploited for Distributed Denial of Service (DDoS) attacks.
Port 19 (chargen)
Character Generator
This port is routinely exploited for Distributed Denial of Service (DDoS) attacks.
Port 25 (unsecured email)
Unsecured SMTP
Mail servers use Simple Mail Transport Protocol (SMTP) to exchange email. We block this to protect upstream bandwidth and prevent customers from running open relays could potentially be used by others to send spam via our network.
Port 135 (epmap)
DCE endpoint resolution
Microsoft has determined that permitting ports 135-139 allows NetBIOS and the Remote Procedure Call to be exploited. The vulnerabilities affect most currently supported Microsoft operating systems.
Port 136 (profile)
PROFILE Naming System
Microsoft has determined that permitting ports 135-139 allows NetBIOS and the Remote Procedure Call to be exploited. The vulnerabilities affect most currently supported Microsoft operating systems.
Port 137 (netbios-ns)
NETBIOS Name Service
Microsoft has determined that permitting ports 135-139 allows NetBIOS and the Remote Procedure Call to be exploited. The vulnerabilities affect most currently supported Microsoft operating systems.
Port 138 (netbios-dgm)
NETBIOS Datagram Service
Microsoft has determined that permitting ports 135-139 allows NetBIOS and the Remote Procedure Call to be exploited. The vulnerabilities affect most currently supported Microsoft operating systems.
Port 139 (netbios-ssn)
NETBIOS Session Service
Microsoft has determined that permitting ports 135-139 allows NetBIOS and the Remote Procedure Call to be exploited. The vulnerabilities affect most currently supported Microsoft operating systems.
Port 445 (Microsoft-ds)
Microsoft-DS
Microsoft has determined that permitting port 445 allows NetBIOS to be exploited. The vulnerabilities affect most currently supported Microsoft operating systems.
Port 520 (routing)
Routing information protocol (RIP)
This port is routinely exploited for Distributed Denial of Service (DDoS) attacks.
Port 593 (http-rpc-epmap)
HTTP RPC Ep Map
Microsoft has determined that permitting port 593 allows Remote Procedure Call to be exploited. The vulnerabilities affect most currently supported Microsoft operating systems.
Port 1433 (ms-sql-s)
Microsoft-SQL-Server
Microsoft and CERT.org determined that external access to Microsoft SQL Servers enables several exploits and vulnerabilities.
Port 1434 (ms-sql-m)
Microsoft-SQL-Monitor
Microsoft and CERT.org determined that external access to Microsoft SQL Servers enables several exploits and vulnerabilities.
Port 1900 (ssdp)
SSDP
Used as part of Universal Plug and Play. This port is routinely exploited for Distributed Denial of Service (DDoS) attacks.
Port 4444 (Trojan UDP & TCP)
Common Malware port for trojans and threats
References:
https://www.spectrum.net/support/internet/blocked-ports/
https://www.cox.com/residential/support/internet-ports-blocked-or-restricted-by-cox.html
https://about.att.com/sites/broadband/network#:~:text=Similar%20to%20our%20blocking%20of,to%20share%20network%20routing%20information