264.6 billion spam messages sent per day, roughly 90% of the overall e-mail traffic over the internet. 10% of spam e-mails with malicious attachments are rigged with malware or carry phishing forms, Bitdefender says. HTML pages (either phishing or commercial offerings), followed by archives (9.6%) and DOC files (6.26%) Other common attachments are made of images, images, XLS spreadsheets; PDF and audio files gathering less than 1% from our spam samples.
Source: https://www.helpnetsecurity.com/2012/04/30/whats-in-your-daily-slice-of-spam/