Posted: 12th Jun, 2004 By: MarkJ
The UK's largest cable operator, NTL, already blocks port 135, yet inbound traffic to 137 (UDP), 138 (UDP), 139 (TCP), 445 (UDP & TCP), 593 (TCP), 1433 (TCP), 1434 (UDP) and 27374 (TCP) has now also been halted:
"This 'port-blocking' should have little or no effect on your use of the Internet but it will significantly reduce the vulnerability to infection from variants of the Welchia and MSBlast worms," NTL explains in a notice to subscribers. Welchia and MSBlast are also known as Nachi and Blaster, respectively. NTL hopes to shepherd users with virus infection to special websites to help them clean their computer.
NTL's measures are a rational response, but the move will create problems for some home users who need to use Windows File and Print Sharing over the Internet or run applications like Exchange at home. This minor inconvenience is considered by NTL to be a price worth paying in the fight against worms.Given the vast and complex nature of the online world, we doubt that it'll just be File and Print Sharing affected.
It's a pity technology doesn't allow clients to control what ports can and can't be blocked via the ISP or without needing to buy your own firewall. More @
The Register.