Spam emails that hide their message within PDF (portable document format) attachments have all but disappeared, according to security experts.
In an attempt to get around spam filters, the message is contained in a PDF file, a format commonly used for documents that contain both text and images.
However, it seems that the tactic has been abandoned by spammers as not enough people are prepared to open the files.
"If PDF spam email messages have all but disappeared, there can only be one reason - they're not working," said Graham Cluley, senior technology consultant for Sophos.
Sophos said that the number of spam messages using this method had dropped to virtually zero from around 30 per cent earlier this month.
"Spammers wouldn't turn away from PDF spam if it was an effective way to fill their pockets with cash and direct consumers to their websites, dodgy goods or dodgy investment opportunities. This drop indicates that the spammers are finding it hard to fool the public into reading marketing messages distributed in this way."
But Cluley did warn that it may not be the last we see of PDF spam.
There could still be more campaigns to come, but its dramatic fall may be a sign that we are witnessing its demise," Cluley said.
www.sophos.com