Spam is again on the rise, led by a flood of junk images that spammers have crafted over the past few months to trick e-mail
filters, according to security vendors.
Called "image-based" spam, these junk images typically do not contain any text, making it harder for filters that look for
known URLs or suspicious words to block them.
Instead of a typed message, users will see only an embedded .gif or .jpeg image file urging them to buy pharmaceuticals or
invest in penny stocks.
Antispam vendor Cloudmark says that half of the incoming spam is now image-based on the "honeypot" systems it puts out on
the Internet to lure spammers. "About a year-and-a-half ago we started seeing a little bit of it, but it wasn't until the
past six months that it became a serious issue for many antispam companies," said Adam O'Donnell, a senior research scientist
with the company.
Image-based spam has jumped from about 1% of all spam messages in June 2005 to around 12% today, according to Craig Sprosts,
senior product manager with IronPort Systems.
Its growth is helping to fuel a global resurgence in spamming, Sprosts said.
The total number of spam messages sent daily is up 40% since April, Sprosts said. Much of this new spam is coming from a "relatively
small group of spammers with control over very large zombie networks," of hijacked computers, he said.
Spammers now generate an estimated 55 billion messages per day, according to IronPort. A year ago that number was 30 billion
e-mail messages per day.
The combination of greater volume and better techniques has meant more complaints for network administrators.
The IDG News Service is a Network World affiliate.
