My employer was hit with malware two months ago and we've contained and treated it. However, it looks like our address book got hijacked. Users are being bombarded every day by spoofed emails using names of our employees, but coming from various domains around the world. Outside customers and vendors we often communicate with are also reporting that they are getting the same type emails, multiple times daily.
I know this is a long shot, but is there anything at all we can do about this? I suppose anybody can type any name in the "From" box on a message and since they have our names and contacts, they are exploiting it. We mark all external emails as [EXTERNAL] so at least people will see that the emails come from outside our domain despite the user's name, but that doesn't help for our vendors, customers, and other contacts.
We currently have Sophos installed on our servers and desktops, and run Barracuda's spam filter. Most of this stuff is getting caught and blocked, but there are so many that a few still slip through.
Any suggestions here?