r3dux.org

My Linux-running laptop seemed to be a little bit sluggish, so I had a look at the amount of free RAM available – and did a double take:

A few apps eating an entire 4GB? Say it ain't so!

This is on a 4GB machine with a web browser (6 tabs) open, email client, code::blocks IDE and totem to play some music. How can that devour my entire 4GB?

Answer: It can’t. Or at least it’s not! The Linux kernel is in fact using free RAM as a disk cache to keep your most often used data in memory and thus speed up the system. As soon as that RAM is actually needed for applications, then it’s instantly made available. This is in theory like the Windows Superfetch service (which is the first thing I disable on any Windows machine I’m forced to co-exist with), only the Linux version actually works well without perpetually thrashing the pants off the hard drive.

What’s really happening is this:

It ain't so =D

For the exact workings, please see the excellent (and indeed excellently named) site “Help! Linux ate my RAM!” – http://www.linuxatemyram.com/.

Bit of a PEBKAC moment, there

Just noting this for future reference, but I finally got iTunes working properly on a Windows PC that would at random:
- transfer some songs to iPod Touch devices successfully,
- transfer some other songs, then crash, then the device reports no music on it, or
- corrupt the device so badly it needed fresh firmware restored.

And the the culprit turned out to be…. Zone Alarm. No kidding. Turn off Zone Alarm and everything worked instantly.

iTunes is still a god-awful PoS though, but at least it’ll now transfer music and apps. If you’re getting “app could not be installed because it is not signed” issues with iTunes, and you’re installing legit apps, chances are that turning off Zone Alarm will fix it right up. Amazing.

Snarky bastards, aren’t they?

I thought my Linux box was pretty safe. I mean, I use a strong password, I have my entire home directory encrypted, I should be alright, yeah? Ummm, no… I’ve been thinking about security a bit recently, and as much as I’ve always had an interest in the topic, it’s not my core field – I’m a software engineer at heart, so I build software, not secure it. But with 2011 being the year of the hack with Anonymous and LulzSec hacking site after site after site, along with the major Sony hacks – it can’t help be anything but my field anymore.

So with a strong password and disk encryption I thought I was safe in case my laptop was stolen – but really it isn’t at all. If you have physical access to a machine, then it’s yours. This definitely comes under the ten laws…

The Ten Immutable Laws of Security

There’s a very good Microsoft article called the Ten Immutable Laws of Security which you can read here. The article discusses each one, but I’ll just list them here:

1. Law #1: If a bad guy can persuade you to run his program on your computer, it’s not your computer anymore.
2. Law #2: If a bad guy can alter the operating system on your computer, it’s not your computer anymore.
3. Law #3: If a bad guy has unrestricted physical access to your computer, it’s not your computer anymore.
4. Law #4: If you allow a bad guy to upload programs to your website, it’s not your website any more.
5. Law #5: Weak passwords trump strong security.
6. Law #6: A computer is only as secure as the administrator is trustworthy.
7. Law #7: Encrypted data is only as secure as the decryption key.
8. Law #8: An out of date virus scanner is only marginally better than no virus scanner at all.
9. Law #9: Absolute anonymity isn’t practical, in real life or on the Web.
10. Law #10: Technology is not a panacea.

There are issues with these “laws” – but you can google that for yourself – what we’re thinking about today is #3 – physical access == potatowned…

Getting it Done

First, reboot the machine and instead of booting as normal, select recovery mode from the GRUB menu:

Next, opt to drop into a root shell:

You don’t need to enter any password at all for the above – you’re just given root access… At which point, you just reset the password for a user account (in this case I created an account called test, but you can reset the root password or the password on any other account just as easily):

That’s it – you own the box. Simply reboot again and log in with the password you just specified.

Safety is an illusion

I’ve got to say, when I first read about this my jaw just dropped – surely it’s not that easy? But it is. So good job on the disk encryption and strong password use, but it’s all for naught. You’re not asked for a root password, or for an account password before you can reset anything – you’re just given full root access because you asked for it nicely. And with a Windows machine you just boot the box from an OphCrack CD and wait a few minutes before it delivers the password via the use of rainbow tables.

Absolutely incredible.

Just stumbled across this and… wow! It didn’t even occur to me that this would be possible.

The future is now, eh?