One of the "prepare for a zero day" steps that I highlighted in my story last week was to inventory your network stations, and know what's running on them.  In short, the first 2 points in the SANS 20 Critical Security Controls.  This can mean lots of things depending on your point of view.

Nmap can make an educated guess on the existence of hosts, their OS and active services:
nmap -p0-65535 -O -sV x.x.x.0/24
Good information, but not "take it to the bank" accuracy.  It'll also take a LONG time to run, you might want to trim down the number of ports being evaluated (or not).  Even if you don't take this info as gospel, it's still good supplemental info, for stations that are not in your domain.  You can kick this up a notch with Nessus (Nessus will also login to stations and enumerate software if you have credentials)

If you're running active directory, you can get a list of hosts using netdom, and a list of apps on each host using WMIC:
netdom.exe query /domain:domainname.com workstation | find /v "List of Workstations" >stations.out

(if you use "server" instead of "workstation", you'll get the server list instead)

and for each station:
wmic product list brief

But having run exactly this recently, this can take a LONG time in a larger domain.  How can we speed this up?  In a word, Powershell.
To inventory a domain:
import-module ActiveDirectory
Get-ADComputer -Filter * -Property * | Format-Table Name,OperatingSystem,OperatingSystemServicePack,OperatingSystemVersion

To inventory the software on a remote workstation:
Get-WmiObject -Class Win32_Product -computername stationnamegoeshere | Select-Object -Property Name

( see here for more info: http://technet.microsoft.com/en-us/library/ee176860.aspx)

I collected this information first using the netdom/wmic way (hours), then using powershell (minutes).  Guess which way I'd recommend?

OK, now we've got what can easily be Megabytes of text.  How do we find out who needs some TLC?  Who's running old or unpatched software?

As an example - who has or does NOT have EMET 4.1 installed?

To check this with WMIC:

"go.cmd" (for some reason all my parent scripts are called "go")  might look like:
@echo off
for /f %%G in (stations.out) do call emetchk.cmd

and emetchk.cmd might look like:
@echo off
echo %1  >> inventory.txt
wmic /node:%1 product where "name like 'EMET%%'" get name, identifyingnumber, InstallDate >> inventory.txt
echo.

Or with powershell, the domain enumeration would look like:
import-module ActiveDirectory
Get-ADComputer -Filter * -Property * | Format-Table Name,OperatingSystem,OperatingSystemServicePack,OperatingSystemVersion  > stations.out

Then, to enumerate the actual applications (for each station in stations.out), you could either use the emetchk.cmd script above, or re-do the thing in powershell (I haven't gotten that far yet, but if any of our readers want to add a script in the comments, I'm sure folks would love to see it!) - in this example the

Get-WmiObject -Class Win32_Product -computername stationname | Select-Object -Property Name > stationname.txt

Done!

If you run this periodically, you can "diff" the results between runs to see what's changed.  Diff is standard in linux, is part of Windows these days also if you install the SFU (services for unix), or you can get a nice diff report in powershell with :

Compare-Object -ReferenceObject (Get-Content c:\path\file01.txt) -DifferenceObject (Get-Content c:\path\file02.txt)

But what about the stations who aren't in our corporate domain?  Even if your domain inventory is solid, you still must sniff network traffic using tools like PVS (from Tenable) or P0F (open source, from http://lcamtuf.coredump.cx/p0f3/) to identify folks who are running old versions of java, flash, air, IE, Firefox (pre-auto update versions mostly) and so on, that aren't in your domain so might get missed in your "traditional" data collection.  Normally these sniffer stations monitor traffic in and out of choke points in the network like firewalls or routers.  We covered this earlier this year here: https://isc.sans.edu/diary.html?date=2013-12-19

I hope this outlines free or close to free solutions to get these tasks done for you.  If you've found other (or better) ways to collect this info without a large cash outlay and/or a multi-week project, please share using our comment form.

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Rob VandenBrink
Metafore