Phone Counter-Measures

I was very interested to read “The gadgets police use to snarf cell phone data” over on ArsTechnica and wondered how long it would be before there were apps that blocked these gadgets, and/or apps which counter-attacked these gadgets with bad data or viruses.

 

iPhone Tracker

I was very curious to see how my iPhone was tracking me so I downloaded the iPhoneTracker application and ran it. And a few things jumped out at me:

• First is that the data was very inaccurate, notably where was not one single ‘dot’ where my iPhone spends 90% of its time, i.e. my home.
• Second is that the data was very incomplete, it missed a number of trips I have taken.
• Third is that the data can be all over the place, for example it has me wandering all over the runways at Miami, taking samples in a grid pattern (presumably the cell towers.)

Hard to see how useful this could be to anyone.

 

 

It has been a long time since I posted something about diving, in fact it has been a very long time since I had been diving until a couple of months ago when a block cancellation opened up room on a boat to the Silver Banks to snorkel with Humpback Whales.

This is a very sought after trip, the whales are on the Silver Banks for the first three months of the year, and the number of people who can visit is strictly controlled (880 people a year).

This was a wonderful trip, and I managed to get a few pictures.

 

Firewalling Data Wierdness

A project I am currently working on requires the download of about 750MB of compressed data every night from about 10 different sites. This data is used to build links to other resources so it would be a ‘bad thing’ if the data was messed up for some reason. The two patterns I have run into so far are that the data is no longer there (file is missing), or that the data is incorrect for some reason (file is truncated.)

So I put in a couple of checks in the script that handles the download. The first is that the data is downloaded to a temporary area before being moved to its final area. The other is that I check the size of the new file against the size of the current file. If the files differ more than a certain percentage in size, the new file is not used and this is flagged. Obviously the threshold will be domain specific and there may be a direction check as well (i.e. the file should never be smaller.)

This is pretty much all I can do, the files don’t have MD5 signatures, and there are no deltas either.

Java Garbage Collection

Lucid Imagination has put together a good primer to garbage collection in Java:

Garbage collection in Java is the processes of freeing the dynamic memory used by objects that are no longer being used by an application. In languages such as or C or C++, the developer is often responsible for managing dynamic memory (using malloc and free or new and delete). However, in Java, this task is left up to something known as the garbage collector. A garbage collector automatically frees unused memory, freeing the developer from much of this thankless memory juggling.

Well worth reading.

Additionally here are some more links:

• Java Tuning White Paper
• Tuning Garbage Collection with the 5.0 Java[tm] Virtual Machine
• Ergonomics in the 5.0 Java[tm] Virtual Machine