2 Bit Hacker

From time to time I think about tricks for managing e-mail, and the other day I came up with an idea I hadn’t seen in practice before. I doubt it’s an original idea, but it seemed interesting to try and implement.

Most people end up using the same e-mail address everywhere, like chip@2bithacker.net. This is easy, it works, and it’s how e-mail was intended to be used in the first place. But you give it to some bad eggs and they sell it to some spammers and now you start getting junk to that address. So what do you do?

In the past, I’ve tried to use local-part extensions to identify who I gave the address to. These are usually things like chip+facebook@2bithacker.net, which many mail servers will treat just like mail sent to chip@2bithacker.net, but you can then filter on the +facebook part. Unfortunately, this is well understood by the spammers as well, so they can easily strip off the +facebook part and go about their business as usual. Also, there are websites out there that don’t think a + can be in an e-mail address, so they won’t accept it. There are various ways around this, of course. One could reconfigure their mail server to use a different characters, such as a dash or period, or even some letter if you wanted to be weird.

I’ve also seen people use virtual domain wildcarding to send any local-part at their domain to a default mailbox. In this case, you could just tell Facebook that your e-mail is facebook@2bithacker.net and it would still wind up in your inbox, and you’d know if Facebook gave your e-mail out to others if you start seeing non-Facebook e-mail coming in to facebook@2bithacker.net. This isn’t great though, as spammers regularly probe addresses trying to find common names to spam at, and with wildcarding, anything @2bithacker.net becomes a valid e-mail address to you.

So I had an idea, mostly building on the second use-case, but with some smarts added in. When signing up for a site, say Facebook, give them an e-mail address of facebook@2bithacker.net as above, but with your mail server configured such that mail to facebook@2bithacker.net is only accepted if facebook appears in the sender’s domain name. So mail to facebook@2bithacker.net is allowed from update@facebookmail.com, but mail from spammer@buystuffnow.com isn’t. In the latter case, the server will send back a 5xx error code just as if the address isn’t valid.

I’ve been trying to come up with a catchy name for this technique, something better than “semi-whitelisting” and I think Sender Domain Local-Part, or SDLP for short, might make sense.

It should be pretty trivial to implement as a Postfix policy server, and I’m working on a reference implementation there to try it out. I suspect it’d be pretty easy to do in Exim as well. I’ll try to remember to post again once I get it working.

I have been unable to find a device by the following specification, but I think it would rather handy to have. I suspect it wouldn’t have a huge appeal however. The device:

A small box with a USB port on one side and VGA, USB, and PS/2 cables coming out the other side. You connect the VGA, USB, and/or PS/2 cables to one computer, and the other USB to another computer, and it gives you a window on your screen that acts as a monitor for the other computer.

I think this would be great for people who have to work on machines in datacenters and the like, where sometimes you just need a monitor and keyboard, but lugging those around are annoying. Just plug this device into the server and your laptop, and poof! your laptop acts like a monitor for the server.

I don’t think it would be terribly hard to implement. You’d need some sort of video capture chip for grabbing the VGA input. PS/2 is basically just a serial output. The USB would just emulate a keyboard and mouse (perhaps via a virtual hub) to the “remote” machine. The other USB would be somewhat trickier, I’m not sure if there’s a standard video transport over USB.

You’d probably be able to sell them to system administrators, PC technitions, and maybe people who want to run a small server at home, but don’t want to switch back and forth all the time with a traditional KVM switch. The closest competeing product I’ve seen is a one-port KVM-over-IP box, which runs $500+. I think an ideal price point for this would be in sub-$100, prolly in the $80-$100 range.

So, there’s the idea, someone go turn it into a product and sell me one…

Now I remember, I was also trying to figure out what I want to do with my tax return. Part of me wants to do the responsible thing and use it to pay off my debt faster or to stick it into my somewhat sad looking savings account, but part of me wants to blow it on something fun like a new laptop or an HDTV or a Mac Mini or something like that.

I was also struck by the thought of registering 2 Bit Hacker as a business with the state, and start actively pushing my consulting a bit more. I think I’ve talked about that in my weblog before. But the thought occurred to me that a new laptop could then be considered a business expense. It would also be a good way of separating out any income I get from doing SimPro maintenance work.