Spammers embrace PDF file attachments

As spam-bearing image files are increasingly weeded out by email filtering systems, spammers are increasingly embedding their messages in PDF file attachments, according to McAfee anti-spam researcher Guy Robers.

Security Focus reports that "image spam" has gone over wholesale to PDF in 2007 - a fact confirmed by the regular arrivals of PDF-bearing mails in the IT Zone junk mail box.

Email security specialists report that PDF files started regularly appearing as spam attachments last month and SecurityFocus estimates that they now account for 2%-7% of junk email.

And because PDFs tend to

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