Fighting malware and spam

Spreadsheets latest spam message carriers

XLS files follow PDFs as junk email ad vector.

After the image spam deluge and the recent wave of spams carrying their messages in PDF files, the latest trend seems to be spreadsheets in Microsoft's XLS format, as used by the popular Excel spreadsheet program.

Numerous campaigns have been reported using the file format to carry standard spam advertising pushing pharmaceuticals and 'pump-and-dump' stocks. Files in the spreadsheet format, in widespread use as a vehicle for business data, are sent as an attachment in an attempt to bypass text-scanning spam filters, but instead of the usual tables of figures the contents are garish advertising, generally strewn with the usual poor grammar and spelling. Some have also been seen using the zip archive format to compress the data and further complicate detection.

Examples of the spammed spreadies can be found at Trend Micro here, at Sophos here and at McAfee here.

25 July 2007

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