THIS IS NEW and NASTY -- Targeted Trojan Email Attacks

The United States Computer Emergency Readiness Team (US-CERT) has received reports of an email based technique for spreading trojan horse programs. A trojan horse is an attack method by which malicious or harmful code is contained inside apparently harmless files. Once opened, the malicious code can collect unauthorized information that can be exploited for various purposes, or permit computers to be used surreptitiously for other malicious activity.

You can read all the details at US-CERT Technical Cyber Security Alert TA05-189A