Monday, April 23, 2012

Threats on OS X


It is said that if you know your enemies and know yourself, you will not be imperiled in a hundred battles; if you do not know your enemies but do know yourself, you will win one and lose one; if you do not know your enemies nor yourself, you will be imperiled in every single battle.
--Sun Tzu

Like every other Mac user who is paying attention this week, I've been reading the stories about malware on OS X (e.g. Ars Technica about Flashback here and here).

Charles Edge's Enterprise Mac Security is a good place to start learning about this stuff (although the book's pub date is 2010 and in places it looks quite a bit older). It's also probably not for the average user.

Some terminology: malware is a comprehensive term for various strategies by which bad guys attack users' machines, including (quoting Edge):

Virus: code attached to a file, which can replicate itself and spread to other files on a computer. A simple virus does not spread over a network without transfer of infected files. [Wikipedia has a somewhat different take.]

Worms: spread across networks by taking advantage of security flaws. [An example is OSX.Leap.A.]

Trojan Horse: these embed themselves in an application and activate only when the app is opened. [The app itself is bad, it disguises its actions from the user.]

Rootkit: a software program written to control an operating system.


I've been running OS X since the beginning (when we left System 9 behind), and I've never had anti-virus software. But recent events made me start thinking about being more proactive.

I download and install a lot of non-Apple, non-App Store software, much of it for bioinformatics. I'm well aware that if I type in my admin password for some evil app, there isn't much protection. Yet I run in admin mode all the time, because I find it a pain to be on a plain account. That's the first thing to change if you're not in the same situation.

The most important aspect of my security policy is that I don't have anything on the computer I can't afford to have stolen. I don't have any banking passwords saved. I could be undone by a Keylogger, but that's about it.

My Sharing Prefs panel consists entirely of unchecked boxes. If you want to share stuff you should definitely read Edge's book or another.

I always do a clean install when I upgrade the OS. I have most data backed up to two different hard drives. I pay attention and always update ASAP.

For my desktop, I have automatic login enabled. If someone has physical access to your machine, you're pretty much hosed anyway. (Unless you want to do FileVault).

I've never been crazy about anti-virus software:

  • the market share argument is MS propaganda and FUD---OS X with no sharing is hard to crack
  • most (all?) Pwn2Own stuff is user account-only, not root (not positive about this, how hard is privilege escalation?)
  • anti-virus never protects against zero-day exploits
  • the AV guys talk a lot to drum up business, like ambulance-chasing, bottom-feeding blood-sucking lawyers

    Nevertheless, the news that the Java exploit somehow got around the requirement for an admin password really worries me. It's not easy to find out how it works (I suppose they don't want copycats). So I'm happy that I don't have Java on my machines running Lion, and I disabled it on the old one.


    I've taken two new steps toward heightened security. I downloaded and am evaluating Little Snitch.


    So far, I haven't seen any evidence of network connections that wouldn't be expected. However, I was a bit surprised to see that many apps (including all Apple apps) phone home each time they are launched (origin of the phrase).

    Also, there are a lot of things (Agents and daemons) doing network stuff that I wasn't aware of---as one example, PubSubAgent.


    This agent checks for updates to your RSS feeds, of which I have none (too old fashioned). At some point recently, a Safari update changed the Pref for this to "automatically update articles in Bookmarks bar". It bothered me because I've been methodical about deleting cookies and website data when I'm done. Yet PubSubAgent wanted to connect to feeds.arstechnica.com. I thought, how would they know about that? before understanding that it's a Safari RSS thing. Anyway, I turned off the reader as a test, and we'll see if PubSubAgent doesn't disappear.

    I heard about Lingon in Edge's book. It's an app for managing LaunchAgents and (I thought from the book) LaunchDaemons.

    Lingon is from Peter Borg, who made (still makes) Smultron. I used Smultron a lot in the days before TextMate, and loved it. So I downloaded the app from the AppStore, but I'm disappointed because it's been crippled. It only works with current user-specific processes and won't show me anything about system stuff.

    One thing it did show me is an automatic Adobe Reader update job. I only installed Reader (300 MB!!) for one time when I had to use it. That job is now deleted.


    The second new tool that I'm working with is ClamAV, an open source anti-virus tool. I read about it here and got it (with a Mac GUI) from here.

    Apparently ClamAV has sucked for OS X in the past, but lately things have changed for the better. Anyway, the scan didn't find anything on my account's files.


    What else should I worry about?

    My Wi-Fi network is not "closed", the name is visible when you scan for networks. This could be a security liability. I don't know if it's possible to do a brute-force password attack on the Airport---something to read up on. But at least I have a decent password. Luckily, I live in a place where very few people drive by.

    My ip address from the isp is supposed to be dynamic, but it's not---hasn't changed forever, as far as I know. Apparently one can force a change by spoofing a new MAC address for the router, but I don't want to do that. Maybe I'll go rummage in the basement for an old router and see what happens.

    Rootkits certainly do exist for OS X. There have been ways to look for them (by scanning hashes of system files for alterations) like this Linux tool.

    I believe that Code Signing should make standard rootkits obsolete. But maybe not, since this is not for "scripts" and such but full-fledged applications. Perhaps a question to apple.stackexchange is in order.

    Finally, I think the advantage has to lie with the offense, in a situation where they cannot themselves be attacked. Structure your defense by asking yourself first: what's the worst that could happen if I did get hacked? And take steps to ameliorate that.

    One last thing. The future of OS X is clearly not good for people like me: my computer will be like my iPhone. Apps can do whatever they want on the network, there's so much network activity (and push stuff), that the user can't make sense of it, but in theory an app will be so completely sandboxed it can't touch the rest of the machine. My programs won't be able to just do whatever they want anymore. Like the impact of barbed-wire fencing on the old West.


    Sorry for the rambling post..


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