One of the biggest worries faced by a computer system administrator is that users are really imposters. As an administrator of a small computer cluster used by scientists, this is the number one issue. How do you detect whether a logged-on user is legitimate? Do you want North Koreans running bomb codes on your supercomputer? Could you tell if they were?

I currently have about 420 GB of 320 kb/s mp3 albums of mostly classical music. Since almost all of these I ripped from my own CDs, a long and laborious task, I have 4 replicas of my collection. This has saved me at least 6 times. I have had a hard disk crash, and a backup disk erased by the restore program! Nowadays, a 2 TB external drive is only $89, so it does not pay to be chintzy about backup storage.

The Barnes & Noble Nook Color (NC) was recently updated to run Android 2.2. It is a svelte, beautiful 7" tablet that is a much more convenient size and weight than, say, an iPad.

But as delivered by B&N, it can't do very much because you can only install apps from the B&N marketplace (all of which seem to cost money).

   There is an old adage: "If it's working, don't change it." Unfortunately, that is bad advice when it comes to computer security. Software is inherently ephemeral, and when a version goes out of support, it must be upgraded or replaced. When a patch appears, it must be applied, and the sooner the better because the bad guys decompile those patches to figure out what to attack.