AT&T DSL Port Blocking Policy

Customers with dynamic IP addresses are blocked by default.

Since 2004, AT&T has blocked several TCP ports to prevent the spread of malicious software like viruses and worms. The AT&T community forum states that customers with static IP addresses can request all ports be unblocked.

Identification

TCP port 25 (outbound) is automatically blocked, as are ports 135, 139, 445 and 1025. Port 25 is used for file sharing and wireless print sharing over the Internet. The other ports are blocked due to virus vulnerabilities in some versions of Windows operating systems.

Considerations

Any blocked ports can be unblocked if you have a static IP address with AT&T. Static IP accounts are generally more expensive than standard dynamic IP accounts. To unblock any port, contact AT&T and request the change.

Prevention/Solution

According to DSLReports.com, it takes 12 to 24 hours for ports to be unblocked and you'll need to log out of the system, turn the router off for at least one minute to reset it, then log back in for the change to take effect.

References

• AT&T Community Forum: DSL Blocking
• DSLReports.com: AT&T Northeast (SNET) DSL FAQ