List of blocked ports

Updated 8/15/2012 4:22:42 PM by Comcast Expert

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

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 465.
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.

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