Among all the confusing posts and scare stories on offer this week about the flashback trojan, a lot of people seem to have missed the instructions for dealing with it.
Here’s F-Secure’s removal procedure:
Here’s Rich Mogull’s general advice for securing your mac in light of this new threat:
It’s also worth emphasizing that, for technical reasons, if your mac has Microsoft Office 2008 or 2011 or Apple’s XCode installed, this particular trojan will not have been able to infect your computer.
If you have reverted your mac to Snow Leopard from Lion, its important that you also remove the Recovery HD, as it can compromise the security of your Snow Leopard installation (for security issues with Lion, see here). Reverting to SL via Time Machine or restoring from a clone will leave the Recovery partition in place, meaning anyone can boot into it and reset your Snow Leopard passwords merely by restarting your mac while holding down the ‘option’ key.
To remove the Recovery disk follow this procedure:
1. Revert back to Snow Leopard using Time Machine or a clone.
2. Once you’re up and running and have confirmed everything is good, go to Terminal (Applications > Utilities > Terminal) and paste/type this command to confirm the presence of the Recovery HD:
then press ‘Return’. If you see a partition labelled something like this
Apple_Boot Recovery HD (see image above)
then you will need to continue with the rest of the procedure. If the Recovery HD is not listed here, you do not have the Recovery partition and need not worry further.
3. If you find the Recovery HD in the list, paste the following command into Terminal:
defaults write com.apple.DiskUtility DUDebugMenuEnabled 1
Now open Disk Utility (Applications > Utilities > Disk Utility). In the menubar at the top, choose Debug > ‘Show every partition’
On the left in the main Disk Utility window, you’ll be able to see ‘Recovery HD’ (it’ll be greyed out). You can click ‘Mount’ in the taskbar to make it active, and you can now delete it using control-click/right click – erase or by using the ‘erase’ tab in DU’s window.
If you want to confirm that the Recovery disk is no longer present, go back to Terminal and type the command from step 2.
how to secure your mac (OS X Lion)
Security in OS X Lion is a big problem that not many people are aware of, and here’s why: your Lion computer contains the install/recovery disk on the internal drive. That means anyone with a basic knowledge of Mac and Lion can start up your mac and reset your passwords, thereby accessing your user accounts and all your personal data. The same trick can help kids easily get round restrictions applied through OS X’s ‘Parental Controls’ feature.
How is this possible, you may ask? First, a little history. Among the 250 changes vaunted about Lion over its predecessor, Snow Leopard, there is one that is widely known but whose implications are rarely pointed out: you download the OS rather than install it from a disc. In the past, if your OS went bad and needed to be recovered, or you forgot your admin passwords, the simplest answer was to insert your install disk. From that, you could restore the OS and reset your passwords. That made your Mac a little safer (though not entirely safe) so long as your disc was kept somewhere physically different from your computer.
With Lion having no install disc, Apple had to find an answer as to how to provide the recovery option. The solution was to install a Recovery partition on the same disk as the operating system itself. In the event that the OS goes bottoms up and needs to be recovered or re-installed, you just restart your computer holding down the ‘command’ and ‘r’ keys to access the Recovery partition.
So far so good, but likewise, just as with the old DVD install discs, you — or anyone else — can also reset the user account passwords from the Recovery partition. That means your passwords are effectively useless. Anyone who wants to hack your user account just has to restart your Mac holding down ‘command’ and ‘r’ and then use the built-in Password Utility to make new passwords for your accounts. Now I’m not going to tell you quite how to do it (you do need a little knowledge to get the user account names and know how to do the reset) but it is widely publicized elsewhere, and indeed even in Apple’s own online documentation (so if you really want to know, google is your friend or follow some of the links in this post…).
What’s the answer to this security nightmare? Here’s one thing that’s NOT the answer but which I have seen widely touted: setting a firmware password. If you’re not familiar with the concept of the firmware password, don’t worry. It is practically useless, since anyone can reset that simply by taking off the back of your computer, and then pulling out and then putting back in one of the memory chips.
Apple, of course, thought about this problem. Their own solution is to encourage you to use FileVault 2 (FV2) to encrypt all your data. Indeed, this is the BEST solution. Without your password, no one can access the disk on your computer no matter what they do (and that includes YOU if you forget it…). However, there are a couple of drawbacks to FV2. One is that it requires extra disk space, and if you have more than one partition on your hard drive, or a lot of data, and little space you may not be able to encrypt and decrypt your data. The other drawback is that FV2 places a little extra wear-and-tear on your hard disk (though that may be negligible given the security pay off).
Using FileVault 2 is really the only security option if you’re using Lion. However, if you don’t have the space for it, there is a ‘second-best’ strategy (see below why it’s only ‘second best’), and that is to remove the recovery disk and use a clone as your recovery option instead (WARNING: the Recovery disk is required for FileVault 2, so by removing it you will also remove the ability to use FV2).
There’s a couple of ways to remove the recovery partition on your internal disk, but this is probably the best:
1. Clone your current system to an external disk using Carbon Copy Cloner. This will clone your entire system exactly as it is now, but it will not copy the Recovery disk.
2. Still booted into your internal OS (the one on your machine), open Terminal.app and paste the following command:
defaults write com.apple.DiskUtility DUDebugMenuEnabled 1
3. Open Disk Utility.app (Applications/Utilities/Disk Utility.app). In the menu bar of Disk Utility, choose Debug > Show Every Partition.
4. In the left-hand pane of Disk Utility, you can now see the Recovery HD. Click on it. Then click on the Erase tab on the (larger) right-hand pane. Click the Erase button down there on the bottom right.
5. Quit Disk Utility.
Now you can use your bootable clone as your recovery disk if your OS becomes corrupt and no one can boot up your computer with ‘command-r’. If you keep the clone backed up on a regular incremental schedule (you can choose anything from once an hour, once a day, week, or month), you can simply restore a corrupted internal disk to exactly the same state as your last backup.
Why only ‘second best’?
As alluded to earlier, it is still possible for advanced users to start up your mac and reset the password without the Recovery partition (this was also true in Snow Leopard even without the install disc). In fact, what this procedure does is give your OS X Lion installation the same security level as an OS X Snow Leopard installation, which is not actually that great, but better than Lion with a Recovery disk! Also, if you are storing highly sensitive data, don’t neglect the fact that someone who has complete unfettered access to your hard drive could even remove the disk and recover the data using special software.
The short story is if you want to be absolutely certain that your data is secure, FileVault 2 is really your only option.
featured picture Security Workstation by digitalhadz