There has been a 67 per cent increase in overall spam volume and a 500 per cent increase in image spam since August, according to vendor Barracuda.

This increase is attributed to a number of trends, including a significant uptake in the number of penny stock promotions and messages pitching diet pills and other drugsaccording to Stephen Pao, vice president of product management for Barracuda Networks.

'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. 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.

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Further Reading:

Spam laws fail to measure up

Spam increases to reach highest point since summer

Investors tricked over stock spam