Of the 264.6 billion spam messages sent daily, 1.14% carry attachments about 300 million of which are malicious. Attachments may come in the form of phishing forms that trick users into typing in credit card credentials for scammers to use whenever they want. MyDoom is known to be used in denial-of-service attacks against antivirus and software producing companies sites. Mytob, Netsky and Bagle worm are among the most persistent pieces of malware to pierce users inboxes.”]
Source: https://www.bitdefender.com/blog/hotforsecurity/spam-with-malicious-attachments-rising/