Barracuda Networks, provider of enterprise-class application security appliances, has announced it has seen a more than 67 percent increase in overall spam volume and a 500 percent increase in image spam since August. This increase is attributed to a number of trends, including a significant uptake in the number of penny stock promotions that has been hitting the millions of inboxes of its more than 35,000 customers worldwide.

"The observed increase in the volume of trading of penny stocks that are hyped in spam emails provides significant financial motivation for speculators to send this type of spam," said Stephen Pao, vice president of product management for Barracuda Networks, adding that the volume of other forms of spam messages have also recently increased, including messages pitching diet pills and other drugs. "Across the board, we are observing more spam and more sophistication in sending the spam."

Simple-text messages can be difficult to detect and block because they are created to look like a legitimate text email. The volume of text spam has particularly increased with the popularity of stock spam because these forms of spam are particularly well-suited for text-only email. The call to action is simply to transact a stock; therefore these emails need not reveal their intent through embedded URLs or HTML tags.

Stopping text-only spam generally requires a rapid tactical response. Obfuscating text spam usually involves misspelling key words or randomly inserting unrelated phrases to throw off spam filters. Sophisticated spammers generally design and test their messages against the current spam definitions of popular spam filters. Therefore, blocking these spam messages engineered to pass through filters requires both early detection of an outbreak and rapid deployment of mitigation strategies.

Barracuda Networks has also reported a considerable climb in the volume of image-based spam, a trend that began more than six months ago. Because developing stock spam that can pass through popular spam filters often requires the spammer to degrade the readability of the messages, stock spam also makes up a significant percentage of image spam.

"Image-based spam has created problems for many solutions that do not have the comprehensive feature set needed to protect against it," said Pao. "Because we saw this growing trend early on, we were able to fully equip the Barracuda Spam Firewall against it and as such, our customers are benefiting from a very low incidence of image-based spam getting through to their inboxes."

In the past three months Barracuda has recorded a nearly 500 percent increase in image-based spam.