chris@UU.NET ("Christopher L. Morrow") writes:
ISP's could block all ports and save everyone the hassle of having an Internet.... (I am just kidding of course)
Two interesting points though:
1) Spammers adapt 2) default insecure OS installs cause problems
3) thoughtless reactionism at isp's does little good and sometimes some harm. take for example port-25 blocking. i've been getting relayprobed all weekend by someone who gets around outbound at&t's tcp/25 SYN blocking by sending their SYN's through a provider who shall remain nameless (except that chris morrow happens to work there :-)) using at&t IP source addresses. i guess they multihomed their host and bind()'d the outbound socket to one interface even while making sure the routing used a different interface. high rocket science? NOT. so if you're going to block tcp/25 SYNs on outbound, please make sure you block SYN/ACK's on input too, or else you just give the spammers a little more work to do instead of a lot more work to do. -- Paul Vixie