Year: 2011

Recently it seems email spam levels have been increasing, reading through the news it seems there is some debate if it is really up or not. Either way, I know that my local mailbox has been getting more spam (specifically more binary attachment spam) lately. As I host my own email server, addressing spam levels is something I can do something about at the server level vs. needing to rely on clever filtering by the client.

Hosting your own email server is a little dumb. I like the challenge, and knowing my data is stored on my computer systems is comforting. Most people should just stick with gmail or similar. If you are stubborn like myself, Ubuntu makes it easy to setup your own mail server. There is of course the other details on getting a ISP that allows you to host a server etc. (exercise left to the reader)

One alternative is to run a local mail server that smarthosts through your ISP (or even Google). It can use fetchmail or similar to suck down email from your various accounts too. This would result in your data on your machines and good spam filtering as you offload that problem to the other mail server (say gmail).

Ok, so you’re dumb like me and while spamassassin is doing an ok job, it’d be nice to stop more spam from hitting your mail server. The solution is greylisting, the Ubuntu community docs make it very simple to setup if you’ve got a postfix based mail system setup already.

The concept behind greylisting is very simple. Spammers are lazy and so is spam software. One of the error codes a mail server can answer back is ‘temporary failure’. Greylisting causes the first attempt to deliver a given email message with a temporary failure code, any properly configured mail server will retry after a short period of time (usually minutes). Spam software can’t be bothered to go back, it’s spraying email across a large number of servers and a large number of addresses – a few failures aren’t important. If you want to know more, I encourage you to read through the whitepaper.

The trade off with greylisting is that normal email can be delayed. Postgrey uses an adaptive whitelist to allow frequent valid email to skip the temporary fail sequence. The place you’ll notice delays is when you reset a password, since the email is likely to come from a mail server you don’t often get email from – so it will be delayed by the temporary fail code.

After a day – spam has dropped to zero, and email is still arriving in my inbox. I did have to “wait” for a password reset email that was delayed by 1041 seconds (a bit more than 17mins), the delay time is due to the sending server retry cadence.

Looking at a year of mail traffic on my server, it doesn’t appear that volumes are up that much.

Looking at the weekly graph shows a spike in rejects (due to greylisting), but if you look closely you can see the drop off on viruses and spam (since greylisting prevents those messages from ever being received and processed).

 

 

 

In my recent post I talked about the problems I had with blu-ray playback and Ubuntu. I’m now happy to report that I can accomplish what I originally set out to do: rip and convert blu-ray discs on my Ubuntu system for playback on my mobile devices.

The solution was provided by an update to makemkv (1.6.13), it now supports bus encryption capable drives (BEC). As I wrote last time, installing makemkv on your Ubuntu system is straight forward if you follow the detailed instructions. If you’re a developer familiar with ‘make‘ and are comfortable doing a bit of unix admin stuff, then it’s easy.

Makemkv is shareware: free to try for 30 days, then if you’ve found it useful you’re asked to pay for it. The purchase price is 50 euros. The key you receive is valid for all platforms and all versions (including future ones). The price may seem steep, but compare it to the cost of a blu-ray playback device or a video game and it starts to be very reasonable. The linux version is in beta, and while it is in beta it is free.

Unlike my previous experience with makemkv being unable to process a blu-ray disc, this version happily detected the movie and gave me simple way to rip the movie (25Gb!). The data is being decrypted on the fly so this cuts the read speed down to 3.6x – resulting in a 36 minute job for the 2 hour movie.

There is an option to stream the movie from the original disc. When I initially tried this with mplayer it worked, but was laggy. Using vlc streaming is smooth, but my version (1.0.6) doesn’t support the trhd audio codec so I get the spanish track. Running mplayer with a larger cache (-cache 8192) results in smoother playback, but the same spanish audio track problem. The ripped version of the movie plays back smoothly under mplayer and vlc with no audio issues.

The main reason I installed a blu-ray player in my PC was to enable me to rip and convert the movies for use on my mobile devices. Handbrake is my tool of choice for this type of conversion.

As you can see, Handbrake is quite happy to convert the ripped video. My system can typically do a DVD in 20 minutes from physical media to mobile format. With blu-ray it seems I’m closer to real time (ie: 2hrs for a 2hr movie) due to the amount of data and the two step process. Still in the end, I’ve got a version of the movie I can take with me when I travel.

For folks interested in reading up on blu-ray and AACS, I came across the specification (pdf).