There are rather effective ways to blacklist IP's that abuse ports. I think there's even a list out there. However, I've been running a BBS server for several years now, and I've rarely felt the need to do anything about any hammering on my ports. The one time I actually had to block anyone with IP rules was no matter what I did, I couldn't get Google to stop crawling FTP day and night. But other than that, I'll occasionally get one or two connects at a time sporadically thoughout the day from all over the world... not only on 23, but 22, 21, 80, you name it. As a parent poster commented, many older services still use 23, and blocking that port at the ISP level would put the hurt on end users to connect. I can certainly think of a few ways around it on older software, but it's nothing the casual end user would want to go through just to use a piece of software. If they're going to block more ports, they need to set up some flags for special businesses or industries. For instance, critical infrastructure businesses could have 23 blocked by default... but as a home user, I expect to pay for the full use of my Internet, not a crippled one. It boggles my mind that there are so many ISP's out there blocking 25; I'm fortunate to have an ISP that does not do that, and I'm able to receive my own email. I think everyone should be able to have that choice.