Mac Operations

Monitoring Apple's XProtect meta feed for changes

Greg had an interesting blog post yesterday on handling Apple’s XProtect Updater mechanism for managed environments, as admins were still scrambling to resolve clients that suddenly had their Java Web Plugin disabled and no newer version available to install that would satisfy Apple’s minimum version requirements defined in its XProtect blacklist (new versions of Java 6 from Apple for OS X 10.6 and Java 7 from Oracle have since been posted).

Maybe you’d like to at the very least know when this has been updated, and what are the nature of the changes. Here’s another example where the strings command proves useful, and it’s quickly obvious what’s going on.

If we look in /System/Library/LaunchDaemons for something related to XProtect, we find Opening it, we see it simply runs the executable at /usr/libexec/XProtectUpdater every 86400 seconds (or 24 hours).

Now, run the strings command on this binary, and see a few telltale methods and values (this is taken from somewhere in the middle):
VPROC_GSK_START_INTERVAL change failed: %lu
SCNetworkReachabilityCreateWithName failed: %s
SCNetworkReachabilitySetCallback failed: %s
SCNetworkReachabilityScheduleWithRunLoop failed: %s
NSURLConnection error: %@
Unexpected status code: %ld
Unable to verify signature: %@
Ignoring new signature plist: Not an increase in version
EEE',' dd MMM yyyy HH':'mm':'ss 'GMT'
Last-modified date is later in time than current date

Taking note of the URL at the top, we can simply curl this URL to see that it’s nothing more than a plaintext XML plist prepended with a security signature (the same signature that’s getting written to XProtect.meta.plist. Looking at the other strings, it’s clear that it’s using the Last-Modified HTTP header to compare this date with the current system date (“Last-modified date is later in time than current date”). It’s also using the Version key in the plist to determine whether the plist available from Apple is more recent than the one already installed.

Note, the “2” in the URL ..xprotect/2/clientConfiguration.plist is what was returned on my Lion machine. Snow Leopard clients look for “1”, Mountain Lion clients look for “3”, and so on.

Now we can throw this plist URL into a site like, and ask it to check this URL once per day and send us an e-mail if it’s changed. We can see the details on the change, and when it was last modified. Update: Given that Apple’s updated this list within hours of new Flash/Java releases and will probably continue to do so, checking daily is probably not frequent enough.

We could also use an application like Jenkins, that already handles polling, jobs, and notifications. The URLTrigger works well for this, and we can simply ask it to track the last modified date of the URL however frequently we’d like, up to the minute if we so wish. From this point on we could write the XProtect.meta.plist file ourselves, package it and automatically push it to test clients, or anything we could dream up.

If we want to extract more information, we can also write a very simple script to do so, put it into a versioning system along with the PluginBlacklist information, etc. This example just prints out the version of the meta plist:

curl -s $URL | awk '/\<\?xml/{i++}i' > /tmp/meta.plist
/usr/libexec/PlistBuddy -c 'Print :meta:Version' /tmp/meta.plist

Lots of ways to solve a trivial problem! I’m not advocating whether or not to take measures to disable the XProtect mechanism on all your managed clients, but this might at least give some ideas on how you can at least be kept up to date with Apple’s new minimum security requirements for plugins, known malware, and anything else Apple will add to XProtect in the future.

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