Want to ruin a security manager’s day? Open an attachment—any unknown attachment will do.

According to a written survey of 200 IT and security managers conducted by Watchguard Technologies at this year’s RSA Conference, about half of all IT managers say the worst security offense a user can commit is opening an unknown attachment.

Opening unknown attachments, of course, is exactly what can launch Microsoft Word and Excel macro viruses, viruses, and worms, as well as Trojan horse software. Given the prevalence of viruses and worms, it’s obvious many users do indeed double-click that attachment. In fact, about 80 percent of respondents indicated a virus had also gotten loose on their network within the last year. Many would be traced back to ill-advised attachment opening.

By Mathew Schwartz at Enterprise Systems.

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