Ultimately, this didn't work out, however, after it confused some users, Ruschill said. That's because Web-based e-mail clients such as Gmail and Yahoo Mail recognize Web addresses and automatically insert clickable links when they see things like Hallmark.com in a message. "We had a totally manual process laid out," he said. "I appreciate what Google and Yahoo have done but on the other side, it was like, 'man it's really confusing.'"

The pain felt over the past few months by the greeting card industry shows how quickly scammers can undermine confidence in what has become a crucial communication tool for many industries.

Because this kind of malicious spam is usually sent from the compromised botnet computers themselves, it costs almost nothing to distribute. But it can take a toll on the reputation and, ultimately, the revenues of companies that are targeted.

"Companies have become more and more reliant upon the Internet and their Internet presence as a way to promote themselves and increase their revenues," said Dave Greenwood, vice president of technical operations with BD-Protect, a company that works with corporations, ISPs, and law enforcement to take down servers that are being used in fraud. "They see the Internet and their online presence as a very important part of their revenue stream, and they do not want to see that revenue stream put at risk."