The Self-Destruct File | Hacker News Reader

The Self-Destruct File

blog.obiefernandez.com

15 pointsfogus14 comments

I don't use full disk encryption, but I do have an encrypted partition that has my .ssh, .pgp, password reminder file, and sensitive customer information. Each time I boot up, I mount this partition. I have soft links in my home directory to .ssh, etc. on this partition.

OS X has the "FileVault" system which encrypts the contents of your home folder. This should include things like SSH keys in ~/.ssh, and so forth. (This is not particularly useful if someone steals your computer while it's on and logged in, of course.)

I think it is better to use a full disk encryption product (which encrypts information) or encrypted disk images (which only encrypt sensitive information) as opposed to FileVault.

FileVault converts your entire home folder into a encrypted disk image. While this is fine for security (no worrying about whether your files are actually encrypted, as long as they are in your home folder), it is bad for usability. When you login or logout, FileVault will either mount and decrypt or encrypt and unmount your home folder/encrypted disk image. Sometimes this process can take several minutes. If your computer runs out of battery (or it is turned off in exasperation), the encrypted disk image can be corrupted. The data within is unrecoverable.

After a brief foray with "DoubleSpace" back in the MS DOS 6.0 days, I vowed not to try such nonsense again for fear of data loss, so I hadn't got around to trying FileVault yet. I only mentioned it because no-one else had and it seems to be an overlooked part of OS X.

That said, encrypted disk images work great on OS X. I'd also suspect there's an interesting way to auto-mount/symlink USB drives into useful places so you have to carry it around with you for anything private to work.

I would use a user account called Administrator, without password. Make this user, and only this one, auto-start a program to do all those things you want it to.

It's better than a .txt because it's easier to hide (you don't have to actually hide it this way) and the person that stole your notebook is more willing to wait a little for the default programs to load than when opening a file, especially a txt one.

When he/she thinks it logged in successfully, the portrait of the thief is already in your inbox and your sensitive files encrypted/deleted.

After physical security, you should secure your data. Tips for Mac users:

1. Using 1Password for random passwords encrypted with a master password

2. Enable FileVault, if the password is entered wrong too many times it will wipe the drive.

3. Password protect your iPhone, set it to remove personal data after too many bad attempts.

4. Never use open WiFi.

2. Enable FileVault, if the password is entered wrong too many times it will wipe the drive.

I've never heard of FileVault wiping the user's encrypted sparse image after too many bad password attempts. Googling gives me nothing. If too many bad passwords do wipe the sparse image, how do I disable that? I have backups, but I don't want anyone to be able to delete my data so easily.

4. Never use open WiFi.

Umm... why? Pretty much every site uses HTTPS or hashes your password in JavaScript before sending it over the wire. Sure there's a chance of HTML injection if the login form is sent over HTTP, but it's a very small one. Unless you're at DEF CON or something, open wifi isn't a major risk. I guess if you're super paranoid, set up a VPN server and connect to it when you're on an untrusted network.

I think the ideal solution is to use FileVault or some sort disk encryption, then also have a cron job runs a script every hour/day/whatever. This script would check a certain URL for a message (say https://your-website/is/my/computer/stolen). If that message says, "yes I am stolen", the script would activate the camera, e-mail the picture to you, and run shred on the drive. Basically a poor man's version of http://www.orbicule.com/undercover/mac/

Full disk encryption. No worries mate.

Perhaps combined with another operating system which performs the tasks mentioned in the article? [Taking a picture, and sending it, the ip address, and anything else interesting/identifying about the network (nmap dumps, nearby access points - assuming that it just connects to any unencrypted one - traceroutes, and so forth), to a predetermined email address].

The 'delete everything sensitive' step would either not be reliable (unlinking all the files) or would take an extremely long time (writing zeroes or noise over all those bytes).

I think you could just flip bits at random positions (probably blockwise to be faster) in those sensitive files. This should corrupt the files pretty quickly.

While encryption may save your data, you can't really brick the computer. Take out hard-disk throw in trash, replace with new 50$ disk, welcome to you're new macbook pro.

I know that Dell in particular can set a password on the BIOS that is extremely non-trivial to bypass. Other hardware makers probably offer similar functionality. Taking this a step further and allowing this to be set from the running OS could be possible, thus effectively bricking the computer (barring access to hardware support channels, but you registered your computer anyway, didn't you?)

I could see a file called "secret_accounts_dont_open.txt" being really attractive to my wife or son. Pass.

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