A Nascent Robotics Culture:Often, the spam you get is the result of months or years of this arms race. For example, spammers of yesteryear started sending images instead of text, so that spam filters looking for text like “viagra” would be fooled. Instead, the image would contain the word “viagra,” but filters would see only an image and let it through. In response, antispam software began tossing e-mails that contained only an image, since spam containing an image typically has some text with it like “check out my pictures from Hawaii” or whatever. Rarely does a real person send just an image….
OK, so there is a reason behind the madness. But how could Quinlan explain the spam I get that contains no advertisement for anything, no links nor images, and instead merely quotes some random passage from Dostoyevsky? Quinlan said there’s no way to know for sure, but the reigning theory among antispam experts is that it’s part of what’s called a “directory harvest attack” in which the spammer tries to figure out if there’s a real person behind a randomly chosen e-mail address. The spammer sends out millions of innocuous e-mails and may get a slightly different response from the mail server if the mail has reached an actual person. Once the spammer has established that certain addresses are valid, he can send his real spam and be sure that he’s reaching an inbox.