Joe Job and SPF

First off, get your mind out of the gutter. A joe job has absolutely nothing to do with what you’re thinking about. It’s email related and it can be a pain in the ass to deal with.

What is a Joe Job?
Joe Job is the term used to describe the act of forging bulk email to appear to the recipient as if the email were coming from the victim. Generally speaking, this term is used to describe an attack of this nature. This is to say that when a spambot or botnet sends a massive amount of email to a victim. The named was coined by an attack launched against http://www.joes.com/ in January of 1997. The perpetrator (SPAMMER) sent a flood of emails from spoofed addresses in a (successful) attempt to enrage the recipients to take action against the company.

Why do I care?
There are many reasons, but I will just cover a few until you get the picture. The main victim of a SPAM attack of this nature ends up having an INBOX full of junk. This junk can potentially include malware, virii, and any number of phishing or scam based attacks. Also, since there is so much email traversing the connection, the bandwidth gets sucked up and depending on the actual amount of SPAM coming in, could render the connection unusable until all the mail is filtered through. The problem comes in when there are thousands of messages, that could take days or even weeks. Since the originating address is spoofed, those who don’t know are going to get very upset with who they *believe* to be responsible for sending the email. The last item I am going to touch on is that the person whose email address was spoofed now has to deal with all the auto-responses and whatever else may automatically come their way. (I think you get the idea).

What I can do?
There is nothing that you can do to completely avoid it besides not using the internet or email. There are some steps that you can take. One of the first things is to take a look at SPF (Sender Policy Framework). To set this up in DNS, you need to do the following:

In your DNS zone file for server.com, you should add something like the following:

server.com.  IN TXT    "v=spf1 a mx -all"
  • v – The version of SPF to use
  • a mx – The DNS attributes permitted to send messages for server.com
  • -all – Reject everything else that does match a or mx

This can also get more in depth depending on the number of email accounts you have and from where. For instance, let’s say your mail server’s name is mail.server.com and you also have email accounts on gmail (gmail.com)and your work email (myjob.com). Your line would look something similar to the following:

server.com.   IN   TXT   "v=spf1 mx a:mail.server.com include:gmail.com include:myjob.com -all"

The a line is saying that mail.server.com is authorized to send mail via your mail server. The include statements are basically saying that everything considered legitimate by either gmail.com or myjob.com should also be considered legitimate by you.

There is a lot more information on configuring SPF. The documentation should be read thoroughly as improperly configured SPF can prevent legitimate email from flowing. For more information of SPF and configuring it, check out:

SPF is just one method that can be used to fight against being a victim of a Joe job. You should always be using some method of SPAM filtering in addition to SPF. Layered security needs to be the approach when locking down any type of server or service.

  • http://www.mobilephoneupdates.com Imran Shakir

    mydomain.com. IN TXT “v=spf1 a mx ~all”

    Here it tells that only allow mx for this domain to deal with emails. What do you think? Let me know if i’m wrong?

    Best Regards

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