NetCetra Client Email Blast: July 23, 2007

PDF spam is set to replace image spam as the scourge of inboxes, according to security experts. They say image spam is finally on the decline, but a new threat that uses an attached PDF file to trick recipients into buying stock in a company is emerging.

Paul Henry, vice president with Secure Computing, said security vendors had succeeded in countering the threat of image spam by tweaking their security software to block it. Image spam has long tricked filters because the message's text is embedded in an image found in an email's body, and filters until recently couldn't decipher images. PDF spam is beginning to take image spam's place. The new threat comes from spammers sending an email message with a PDF attached - which most spam filters can't read - that attempts to convince the recipient to purchase stocks.

So far, PDF spam isn't approaching the volumes that image spam has enjoyed - Secure Computing's Henry says in early July it accounted for about 4 percent of all spam sent - yet this new spam trick could prove to be significantly more malicious. PDF spam does hold some potential for spammers who are advanced enough to take advantage of the technology, some say.