ShieldsUp reports Port 25 "closed" on brand new Linksys N750 router

Question

I have a brand new Linksys N750 WIFI router. I tested the ports via the ShieldsUp! test at GRC.com and it reported Port 25 (smtp) as "closed" instead of stealth.

I took a look through the the various pages in the router's web based admin interface, and I don't see anything related to Port 25.

How do I get the N750 to be stealth on Port 25 instead of responding to attempted connections as "closed" ?

Answer 1

Have a listen to Security Now podcast #397. In the episode they talk about how ISP are blocking port 25 (among others including 135, 137, etc.) and are making it return as closed instead of stealth.

Many big ISPs including Comcast, Cox and Verizon are blocking port 25 and there really isn't anything you can do about it, but there really isn't anything to worry about either.