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Support XFINITY Internet List of Blocked Ports

Introduction

Find out which ports are blocked by XFINITY and Comcast services, and why.

Find the Reasons for Blocking Listed Below

Port

Transport

Protocol

Inbound/

Outbound

Reason for block

25

TCP

SMTP

Both

Port 25 is unsecured, and Botnet spammers can use it to send spam. This does not affect XFINITY Connect usage. We recommend configuring your email program to use port 587.

68

UDP

BOOTP, DHCP

Inbound

UDP Port 68, which is used to obtain dynamic Internet Protocol (IP) address information from our dynamic host configuration protocol (DHCP) server, is vulnerable to malicious hacks.

135-139

TCP/UDP

NetBios

Both

NetBios services allow file sharing over networks. When improperly configured, ports 135-139 can expose critical system files or give full file system access (run, delete, copy) to any malicious intruder connected to the network.

161-162 TCP/UDP SNMP Both SNMP is vulnerable to reflected amplification distributed denial of service (DDoS) attacks.

445

TCP

MS-DS, SMB

Both

Port 445 is vulnerable to attacks, exploits and malware such as the Sasser and Nimda worms.

520

TCP/UDP

RIP

Both

Port 520 is vulnerable to malicious route updates, which provides several attack possibilities.

1080

TCP

SOCKS

Inbound

Port 1080 is vulnerable to, among others, viruses, worms and DoS attacks.

Find this article at:

http://customer.comcast.com/help-and-support/internet/list-of-blocked-ports/