One recent campaign circulated via e-mail contains a GIF animation set to flash 'BUY' every 15 seconds which SophosLabs compares to subliminal advertising and political campaigns.

A SophosLabs official said that while pump-and-dump campaigns account for about 15 percent of spam (up 0.8 percent from January 2005), the use of GIF images in stock market spam has risen almost 17 percent since January (18.2 percent) this year.

SophosLabs senior technology consultant Graham Cluley said the use of animations to circumvent spam filters that identify character recognition is used globally and in multiple languages.

"Animated graphics are being used in image spam campaigns to try and weave past filters which may be attempting optical character recognition to decipher the messages that spammers send," Cluley said.

"We have seen image spam being used around the world - not just in English, but languages such as Russian and Italian; it's likely that more spam will use the technique to try and get past gateway filters.