A report claimed spam is back on the increase with levels not experienced since early 2007 - with increased targeting of free hosted services like Google Docs.
The MessageLabs Intelligence Report for May said that levels had reached 76.8 per cent of all emails (71.3 per cent in the UK). It was suggested the high figure was due to changes in tactics by spammers.
The report said there was a move away from reliance on new and undetectable email attachments (switching between image, PDF, MP3, office DOC and XLS spam). The trend was now moving towards taking advantage of open and free mainstream services such as Google Docs and Calendar.
Links to the Google Docs domain were not blocked by traditional spam filters and the environment carried enough bandwidth to host spammer's websites. It was also said to be possible to track their success by the use of Google Analytics.
"The spammers are taking advantage of the fact that these services are free, provide ample bandwidth and are rarely blacklisted," said Mark Sunner, MessageLabs chief security analyst.
"This is one more addition to the growing list of ways the spammers have succeeded in outsmarting traditional detection devices."
Spam levels rose across all industry sectors in May with manufacturing the top for spam activity at 83.7 per cent of all emails. The highest rise was in the non-profit sector, where spam levels grew by seven per cent to 81.3 per cent.
