Ports That Are Blocked by Verizon

By Rob Callahan

Networked devices use specific ports, which can be blocked by service providers.
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Different Internet and communication applications make use of specific ports in order to communicate with other machines on the Internet. In order to limit bandwidth use or curtail the illegal or malicious use of the Internet, many Internet service providers (ISPs) block the common ports used for certain applications. Verizon sometimes makes use of this practice.

Port 80

Port 80 is commonly used by individuals to host servers and websites from their homes. Many ISPs make blocking this port a standard policy. Verizon has changed its policy regarding port 80 several times. While Verizon allowed business accounts with static IP addresses access to communications via this port, residential customers and those with dynamic IP addresses found inbound port 80 blocked prior to 2009. Since then, network upgrades have opened access to this port for some consumers, but the upgrades in question did not occur for all customers at once.

Port 25

Many common email viruses make use of port 25 to infect other computers. Because of this danger, Verizon has sometimes blocked outbound port 25. This block is sometimes removed, but was reinstated as recently as 2010. Inbound port 25 has sometimes been left open while its corresponding outbound port is blocked, as the primary purpose of the block is to prevent outbound email from infecting other computers.

P2P Ports

While some other ISPs have blocked access to the ports which commonly facilitate peer-to-peer connections, such as file sharing networks and BitTorrent services, Verizon maintained a policy of leaving these ports open to its customers as of late 2010. This policy has come under scrutiny due to the controversy and potential for misuse associated with P2P networks. The potential for policy changes and possible blocking of other ports has been hinted at in some public announcements, such as a 2010 joint pact on net neutrality by Verizon and Google.