Fighting Spam (without filters)

There are now some excellent tools to stop spam. I don't mean spam filters, which are being overwhelmed these days. I no longer get spam, what a relief! Below is a description of what works for me. In particular, disposable email addresses have been a godsend. That being said, it is certainly possible to keep spam away by never putting your address on the web and never supplying it to retailers. This is the best method by far.
Note that the links to javascript files will work within the UR math department. If you are not in the department, please copy these files to your own machine, and link to the copies.

Hiding Addresses on Web Pages.

If you put your address on a web page, spammers will find it. Do a Google search for your address; you'll be surprised. It's not hard to hide addresses using javascript or images. With the javascript method, people who visit your page won't be inconvenienced, since they'll see the usual "mailto:" link. However, robots will just see some code. For more information on hiding addresses in web pages, see http://www.turnstep.com/Spambot/html.html, or do a Google search. I've taken some of my suggestions from this and other pages.

Hiding addresses with Javascript

Example: von_neumannmath

It looks like robots can harvest this address. However, the page source just contains some javascript code which produces the address. This recipe uses ideas of Marko Samastur.

On your web page, after 

</head>
put 
<script type="text/javascript" src="/antispam/address.js"></script>
Then, where you want an email link to appear, put 
<span class="justify">von_neumannmath</span>
and replace "von_neumann" with your own id. What will appear is an email link to your address. Note that I have added "math" at the end of "von_neumann" to further disguise it. You don't have to do this, but the script will strip off "math" if it is there. As you see, the page source doesn't contain an address, so robots can't find it unless they run javascript. That's too much work for spammers.

If you have an address outside the math.rochester.edu domain, say mail.rochester.edu, put 

<span class="expand">von_neumannmath mail rochester edumath</span>
Note that you can add "math" both after the ID "von_neumann" and after the final "edu", although you don't have to.

Hoss' Javascript Method

Hoss Firooznia, the UR math department computer administrator, has set up our department web pages so that you can hide an address as follows. 
<span class="eaddr">von_neumann at math dot rochester dot e d u</span>
Observe how you can space out the "edu". Some people believe that spammers are searching web pages for phrases like "at", "dot", and "edu", knowing that this is a common way to hide addresses. This could just be an urban legend, I don't know.

An alternative Javascript method

As before, put a link to a javascript file, but a different one. 
<script type="text/javascript" src="/antispam/antispam.js"></script>
Where you want an email link to appear, put 
<script>
enscramble("von_neumannmath")
</script>
Note that "math" has been added at the end, although it isn"t required. As in the previous recipe, for the full email address, you can write 
<script>
encode("von_neumannmath", "mail", "rochester", "edumath")
</script>
Note that you can add "math" both after the ID "von_neumann" and after the final "edu", although you don't have to.

Hiding addresses in images

This is a simple and effective way to avoid spam. But people will have to copy your address by hand. You can create such an image using the Gimp or almost any image manipulation program.

Here is an example of how to imbed an image into html. 

<img src="address.gif" alt="My email address" />
and the corresponding image:
Email Address

Hiding email addresses in tables

The following table should hide your email address, since the rows are not in the usual order. The code is given below the table.
von_neumann Send me email
@ math.rochester.edu 
<table cellpadding="1" cellspacing="1" border="4">
  <tr>
   <th rowspan="2" valign="bottom">von_neumann</th>
   <th align="left" colspan="2">Send me email</th>
  </tr>
  <tr>
   <th>@</th>
   <th valign="bottom">math.rochester.edu</th>
  </tr>
</table>

Spam-free with Disposable Email Addresses

This method has completely stopped spam for me, saving countless sessions of churning through junk email. Thank goodness! The idea is to switch to a new email address when your old one starts getting spam. There are several ways to do this without much trouble. By the way, my new address is still clean more than a year after I switched. Don't forget to update your address at banks and mailing lists.

Get a New Address

Unfortunately, if spammers have found your address, you may have to get a new address. This is inconvenient, but I've been able to keep several email addresses completely spam free for several years now. Occasionally African spammers using the money transfer scam have found my address by looking at my page, I guess, but I don't reply and they haven't bothered me again, nor have they sold my address to others. This has happened only a handful of times. Actually, I recently had trouble, but after reshuffling my system, I'm spam free again. It's nice.

Commercial Disposable Email Services

Don't give online stores your real email address; you can't trust them! I've even had trouble with banks, so I never give these organizations my real email address. Disposable email services allow you to use external email addresses, and the mail will be forwarded to your permanent address. When one disposable address starts getting spam, it's easy to retire that address and generate a new one. You need never switch your real address. You can easily generate large numbers of disposable addresses. Some services are free, and others even send out messages with new disposable addresses to people sending mail to addresses which you've retired.

I've had good luck with e4ward.com. Also, for $20 a year, yahoo mail plus provides disposable email addresses and forwarding.

Here are two lists of commercial disposable email addresses.
http://techgerm.com/2008/09/24/disposable-email-addresses/
http://email.about.com/cs/dispaddrrevs/tp/disposable.htm

Disposable addresses in Unix

There is also a Unix trick involving putting a "+" sign in your address. Basically, everything after the "+" and before the "@" is ignored by the unix mail receiver. For example, if your address was xxx@yyy.com then all mail sent to xxx+anything@yyy.com would be delivered to you. You can create a script to further process the mail based on what comes after the "+". I've found that some servers have trouble with the "+" sign, so I may have lost some mail. Also, most administrators don't allow mail scripts, due to the possibility of mail loops. We don't allow it here in the math department.

For a price, Yahoo mail will let you set up addresses that use the "-" sign instead of the "+" sign. I've found that these cause less trouble.

Challenge-response systems

Recently I've revived some spam-encumbered addresses by forwarding to bluebottle.com, a commercial challenge-response system. Anyone who sends an email will get a reply asking them to click on a link, and only then will their messages be accepted. You can import your contact list, and then your contacts can email you with no problems. You could do some of this yourself with mail filters, but it's much easier with Bluebottle. OK, it makes some work for people who want to contact you, but it allowed me to revive an address which I couldn't use at all. The big problem with this system is that spammers may send mail with a fake return address which is on your whitelist. Therefore, I'm only using this system as an emergency measure, to revive an address which I couldn't use. Read more about challenge-reponse systems here.