According to the SpamHaus Project--a U.K.-based antispam compiler of blacklists that block 8 billion messages a day -- a new piece of malicious software has been created that takes over a PC for the purpose of sending spam.

This "zombie" computer is then used to send spam via the mail server of the computer’s ISP. This means the spam appears to come from the ISP not the computer itself, making it very hard for an antispam blacklist to block it.

Previously, zombie PCs have been used as mail servers themselves, sending spam e-mails directly to recipients.

This appears to be an obvious evolution of attack vectors from the spammers to overcome the blacklisting methods of spam fighters.
 

ISPs in the United States may have already been hit. Apparently there has been a surge in spam coming from major ISPs.

This will cause serious problems for the e-mail infrastructure, as it is impractical to block mail with domain names from large ISPs.
 

Some people feel the e-mail infrastructure is beginning to fail. Two years on and the can-spam legislation in the United States appears to have done nothing to halt the growth of the biggest burden to the worlds largest infrastructure.

If it continues it could very soon be the beginning of the e-mail meltdown.