Stolen identity- My email account used by hijacker

[macintoch]

A week ago I sent an email to more than 50 colleagues. I have their contact information in my Filemaker database, so I automatically created the messages from this application which transfer them to Entourage and sent from there. The problem is that somehow during the process, a hijacker got my connection and sent SPAM using my email account. I realized this when I started receiving many system notifications of returned mail I have not sent. I have the Firewall activated, which comes with the system, and it allows only for Personal File Sharing and Printer sharing. Also, the Internet Sharing is off.
Can anyone help me prevent this from happening again?

 

[CanadaRAM]

Almost certainly, your email account has NOT been hijacked.

What is happening is called a "Joe-Job" -- it's when spammers forge a known-good email address (yours) as the From: address in their outgoing spam. They accomplish several things: the From: address validates on mail servers that do a reverse lookup, so their spam gets past that filter, and then they don't get all the bounce messages (you do). When filters are set up to block the address, they simply switch the next day to some other poor sod's email address and carry on.

Your address was probably randomly selected from a list of millions of email addresses.

There's not much you can do about this, other than to advise your ISP that a Joe-job is currently being done on your email address, and they can expect to see a higher rate of bounce messages. They will be able to confirm for you that these messages are not being sent through your actual account. On occasion, idiot postmasters will beef and complain to your ISP about you the 'spammer'. Your ISP should be able to tell them to get a clue about forged mail headers.

If the incoming flood of bounces is too much to handle, set up some filters or rules to reject or trash mail from "postmaster" "Mailer daemon" and other common From and Subject terms.

It will likely stop in a day or three.

 

[macintoch]

Thank you, CanadaRAM;5386337. You are right, I have not received any more returned mail in the last days. But I still feel very bad because they (spammers) get their way around and feel sorry for the people like us, who hate spam and are defenceless.