Spam volume worldwide has doubled in the last year, according to Ironport, a spam-filtering firm, and unsolicited e-mail now accounts for more than nine of every ten messages sent over the Internet.
The upsurge reverses a recent trend. According to the Federal Trade Commission, the volume of spam declined in the first eight months of 2005, as antispam software for companies and individuals became increasingly effective. For a time, antispam companies fought spam with some success through three filtering strategies. Their software scanned each e-mail and looked at whom the message was coming from, what words it contained, and which Web sites it linked to.
But spammers have come back with a vengeance. They’ve effectively thwarted the first strategy—analyzing the reputation of the sender—by conscripting vast networks of computers belonging to users who unknowingly downloaded viruses and other rogue programs. The infected computers begin sending out spam without the knowledge of their owners, making it difficult for companies to rely on blacklists of known junk e-mail distributors. Also, by using other people’s computers to scatter their e-mail across the Internet, spammers vastly increase the number of messages they can send out, without having to pay for the data traffic they generate.
Image spam, in which the words of the advertisement are part of a picture, has foiled the second strategy of analyzing the content of an incoming message. Traditional antispam software examines the words in a text message and, using statistical techniques, determines if the words are more likely to make up a legitimate message or a piece of spam. By putting their words inside the image, spammers have moved their message into the software’s blind spot, since it doesn’t analyze images. Image spam increased fourfold from 2005 and now represents 25 to 45 percent of all junk e-mail, Ironport says.
In response, the filtering companies tried optical character recognition, which scans the images in an e-mail and tries to recognize any letters or words. Spammers in turn littered their images with speckles, polka dots, and background bouquets of color, which confuse the computer scanners.
Spammers have also figured out ways to evade another common antispam technique: identifying and blocking multiple copies of the same message. Antispam companies achieved early victories against spam by recognizing unwanted e-mail as soon as it hit the Internet, noting its “fingerprint” and stopping every subsequent copy. Spammers have defied that technique by writing software that automatically changes a few pixels in each image.
The Federal Trade Commission has brought many of cases against such fraudsters over the years. But as a result of the Can-Spam Act, which forced domestic e-mail marketers to either give up the practice or risk jail, most active spammers now operate beyond the reach of American law enforcement. Antispam researchers say the current spam hot spots are in Russia, Eastern Europe, and Asia.
Significance: The Can-Spam Act has created a vast gulf between legitimate e-mail marketers and spammers. At this point, one might think that “scam spam” is readily identifiable, but recent studies show that there are still enough gullible consumers online to make spam that sells items such as penny stock worthwhile, especially since the costs involved in a spam campaign are so low.