A friend left a laptop in an airport bathroom. The computer didn't have a password, and the owner didn't have a backup, and didn't have the serial number of the computer. Please don't let this happen to you.

You are responsible for the security of your personal computer. Nobody else can do it all for you. The major threats are:

1. Theft of a portable computer while traveling.
2. Theft of a computer from your home.
3. Theft and misuse of the information on your computer.
4. Loss of your whole house and the computers in it.

Backup

The information on your computer should be backed up. You should also keep records of the model number and serial number of your computer, someplace besides on the computer. (I keep all this info in a spreadsheet file, with copies in multiple places.)

Passwords

Every computer should have a password. This will help prevent an identity thief from getting at your bank account numbers and personal details, and make your machine less valuable to a physical thief.

Disk Encryption

OS X 10.7 ("Lion") supports full disk encryption. When I install it, I intend to enable this feature.

Tracking Software

The Apple iCloud service provides a feature called Find My Mac to users of OS X 10.7 (Lion). It works like Find My iPhone, but since Macs do not have built-in GPS, it locates the machine using Wi-Fi. Once a missing Mac is located, the owner can remotely lock it, wipe it, send a message or play a sound.

You can download and install  Adeona (free). It sends a secure message with the computer's Internet location to the web every so often, and snaps a picture of who's using the computer. If your computer is lost or stolen, this will help get it back. There is another program called  Undercover ($49), which will sample the WiFi environment and post the geographic location of your computer. The LoJack people also have a similar product, as does  GadgetTrak. New products like this are announced all the time. Use Google.

Identifying Your Computer

Attach a label to the outside of your Mac with your address and phone. I just tape my business card to my computer. (This will also make putting your machine through airport security safer.) Put a luggage tag on your laptop bag too, with your business card.

You can change your Mac so that the "login window" shows a custom message. Mine says "property of ..." with my name, address and phone. In Lion, the custom login screen text can be changed by opening  ► System Preferences ► Security & Privacy ► General. Enter your message in the Show a message when the screen is locked text box.

In older versions of the OS, open a Terminal window and do

sudo defaults write /Library/Preferences/com.apple.loginwindow  LoginwindowText "Warning Text"

This is where DoD laptops say US GOVERNMENT PROPERTY etc etc. Lion also allows you to create a .txt or .rtf document named /Library/Security/PolicyBanner that requires a click.

Locking Cable

In 20 years of carrying laptops, I have never used one of those cable locks that hooks the computer to a desk. Maybe one would work for you.

Special Account for Airport Scan

(I will have to re-think this question when I install Lion and go to full disk encryption.)

A login password on your Mac will make it inconvenient for a thief. But when you go through X-ray at the airport, the border patrol can ask you to boot the computer, to prove that it is not a cleverly disguised salami.

What I do is to create an extra (non admin) account on my computer, and set that account to automatically log in when the computer boots, using  ► System Preferences ► Accounts. The special account's desktop has a desktop picture with my photo, address, and phone, so that it is immediately obvious that it's mine. I enabled "parental controls" on the account so it can't do much.

The special account has a few files in it and will probably satisfy the border patrol.

When I restart my computer, I must take an extra step to get into my real account: start the computer, immediately log out, and log in to my "real" account. I have set the login window so it doesn't show the possible accounts and ask me to choose: instead, I have to know the name of the account I am logging into, and its password.

Here is a  useful document by the Electronic Frontier Foundation on the scanning of laptops at US borders.

Non-Computer Security

A few more things to think about.

• A confetti shredder for paper documents that contain personal information.
• An inventory of your posessions, with serial numbers and costs, stored securely outside the house.
• Fire, flood, earthquake and hurricane insurance.