I once held a meeting with a large cigarette manufacturer. My company was managing their mail gateway and had spam, av and phishing protection in place. They had complained that some spam was still getting through. At the meeting we presented a simple chart showing, of the mail arriving at the gateway, only 2% was deemed legitimate and sent on the the recipient. We advised that turning up the filter was start to result in some legitimate traffic being blocked. These stats from Duke University actually look quite ‘mild’ to me…:
[…] According to Duke’s IT Security Office, about 90 million emails were sent to Duke email addresses in August of this year. About 60 million of them were spam or phishing attempts and blocked.