Although the web has long since eclipsed email as the primary vector for distributing malware, threats spread through email attachments and embedded links have never stopped, and both saw a resurgence in 2009 that continued into the first half of 2010.
Top 10 malware spreading via email attachment, January–June 2010
Source: SophosLabs
Email malware attacks traditionally draw users in with exciting or controversial subject lines, then provide either embedded links or attached files for further information. Inevitably, these links lead to sites pushing malware via exploits while the attachments either are Trojans or use vulnerabilities in Office or PDF viewing software to execute malicious code.