TECHNICAL SUPPORT
Information: Info-Ports blocked or restricted by Suddenlink
► Summary:
The following information describes why certain ports are blocked or restricted by Suddenlink High Speed Internet.
► Content
Reasons For Filtering Ports
·
Protecting our customers - Certain ports are filtered to protect our customers. We can protect against
certain common worms and from dangerous services on our customers' computers that could allow intruders
access.
·
Protecting our upstream bandwidth - Upstream bandwidth to a cable plant is limited. If customers
overuse their upstream bandwidth by running high-traffic servers or becoming infected with a worm or virus,
it can degrade the service of other customers on that node.
·
Protecting the rest of the Internet - Some filters prevent our customers from attacking other computers on
the Internet. In addition to being in our best interests for protecting our bandwidth, it is our responsibility to
prevent abuse of our network.
Port
Transport
Protocol
Direction
Reason for Filtering
25
TCP
SMTP
Both*
SMTP Relays,
80
TCP
HTTP
Inbound
Web Servers, Worms, Net Send
135
UDP
NetBios
Both
Spam / Pop-ups, Worms
136-139
UDP, TCP
NetBios
Both
Network Neighborhood, Worms
445
TCP
MS-DS / NetBios
Both
Network Neighborhood, Worms
1443
TCP
MS-SQL
Inbound
Worms, Trojans
1434
UDP
MS-SQL
Inbound
Worms, SQLslammer
1900
UDP
MS-DS / NetBios
Both
Network Neighborhood
TCP
Subseven
Both
SubSeven
Trojan
*SMTP is only permitted outbound to Suddenlink-provided SMTP servers
Detailed Explanations Of Filtered Ports
Mail servers use Simple Mail Transport Protocol (SMTP) to exchange email. We block
25/TCP SMTP
this to protect upstream bandwidth and prevent customers from running open relays
could potentially be used by others to send spam via our network
Web browsers use Hypertext Transport Protocol (HTTP) to communicate with web
servers. In addition to protecting bandwidth by preventing customers from running
80 / TCP HTTP
high-traffic web servers, we can stop many destructive worms that spread through
security holes in web server software.
NetBIOS (also known as Server Message Block, LanManager, and Common Internet
135, 137 / UDP
File System) is a networked file sharing protocol. The Microsoft Windows "Network
135, 139 / TCP,
Neighborhood" runs over NetBIOS. We filter these ports to protect customers from
445 MS-DC
exposing files on their computers, and to block worms which spread through open
NetBIOS
file shares. The latest addition to this series, a consolidated service port (TCP445),
has also opened new similar security risks in Win2K and WinXP.
Microsoft SQL Server is a database application with a long history of security
1433/TCP,
exploits, and is noted for the propagation of the SQLslammer worm. These ports are
1434/UDP MS-SQL
filtered to prevent exploitation and propagation of such MS-SQL exploits.
discovery/SSDP is a service that runs by default on WinXP. It creates an immediately
exploitable security vulnerability for any network. Filtering this port proactively
1900/UDP - UPnP
prevents XP systems from being remotely compromised by malicious worms or
intruders.
► Applies To
·
Online safety, protecting your computer and our network.
·
More about spyware,adware,trojan horses,parasites and other viruses.
·
More about how to protect yourself against viruses.
