It’s the other end of the threat spectrum: Instead of a massive attack on hundreds of your users, it’s one message, sent to a single user, containing a backdoor Trojan — or worse. Such narrowly-targeted attacks are becoming more popular than ever, according to a new report issued today by MessageLabs. The messaging security company says it identified 716 emails in 249 targeted attacks last month. Most of the email attacks came in the form of malware hidden in a Microsoft Office document. Some 45 percent of the attachments were PowerPoint; 35 percent were MS Word files.