In a “normal” world, a medium-large ISP uses 8 terrabits traffic; in the same time, it deals with 45.000 spams and around 200.000 port scannings and violations of all kind.

As you probably already know, these attacks are not only pointed against ISPs, but it’s clients also.The most frequent violations are connected to protocols like: NetBIOS, RPC, DNS, NFS, telnet, FTP, IMAP.
Maybe it’s time you asked your ISP to give you more options related to security. An ISP can block the attacks or it can use an antivirus which scans the email.

The question is: are you willing to pay more, for a better service?