Category Archives: Computer Science

What is an air gapped Computer?

An air gapped (aka Air Walled) computer is essentially a technique for keeping a computer or network secure.  This is usually done by keeping the computer off the network physically.

This can be done to keep sensitive data on the Air gapped computer or network from being compromised, but can also be done to keep another network safe from an unknown network.

Examples from wikipedia follow:

  • Military/governmental computer networks/systems;
  • Financial computer systems, such as stock exchanges;
  • Industrial control systems, such as SCADA in Oil & Gas fields;
  • Life-critical systems, such as: Controls of nuclear power plants;
  • Computers used in aviation, such as FADECs and avionics;
  • Computerized medical equipment;
  • Very simple systems, where there is no need to compromise security in the first place, such as: The engine control unit in an automobile;
  • A digital thermostat for temperature and compressor regulation in home HVAC and refrigeration systems;
  • Electronic sprinkler controls for watering of lawns.

This Air gapping was discussed on the HBO series The Newsroom during the first episode of the third season, called Boston,  where some whistleblower trying to give Neal classified documents asks him to get an “air gapped computer.”  In the show they describe this as a computer that is not and has never been connected to a network. While this is not inaccurate, you can see above that there are other scenarios that qualify.

 

Filtering a range of IP addresses from Google Analytics

In order to exclude false site visits from my Google Analytics, I have implemented a filter that excludes everything from an IP address range.

First, I check my IP address.  I used my “WAN” ip address since that’s what Google sees when I visit my site.  I don’t have a static IP so this will likely change over time.

Screenshot 2014-10-27 17.13.01

Now that I know my current IPaddress… what is the IP allocation range for ViaSat? Lets look at ARIN (American Registry for Internet Numbers), for the answer…

Screenshot 2014-10-27 17.46.29

This gives us a nice range of 131,072(2x256x256) IPv4 addresses.   I decided to just filter out anyone who is coming in over ViaSat’s ip range.  Sorry ViaSat visitors but your only being filtered from Analytics, so this isn’t such a big deal.

Log in to your Google Analytics account, then click on Admin.  Click “All Filters” then click “New Filter.”   Give it a name, then select “Custom” filter type.

Select “IP Address” in the Filter Field if it’s not already.  Then in the “filter Pattern” text box, you put a “regular expression” that suits the range you want.  In this case I am doing

^184\.(2[0-1])\.([0-9]|[1-9][0-9]|1([0-9][0-9])|2([0-4][0-9]|5[0-5]))\.([0-9]|[1-9][0-9]|1([0-9][0-9])|2([0-4][0-9]|5[0-5]))$

This should exclude the range from 184.20.0.0 to 184.21.255.255

I used the free IP address range regex generator from Analyticsmarket.com

Hope this helps someone.

Setup Dropbox to sync on a schedule

click here for the Mac version

Currently I am living in a part of rural Virginia, where the only option for internet is ViaSat internet satellite.  The service has its ups and downs, but the worst part are the data caps, and they are cell phone low.  In fact the highest plan I can buy is 25GB of data transfer and that is about $140 per month.

One thing that I really miss is the ability to have my Dropbox synced at all times.  The data transfers can be high if I am putting videos and photos into my Dropbox.  Dropbox’s application currently allows you to throttle the bandwidth, but it’s either on or off…

ViaSat does offer something nice…  every morning from Midnight to 5AM they shut off the meters allowing unlimited usage.  I decided to leverage this and make Dropbox sync only during this free window.

Doing this boils down to three things.

1.  Find the Windows Task Scheduler.
2.  Schedule a daily task to START Dropbox.exe at 12AM.
3.  Schedule a daily task to STOP Dropbox.exe at 5AM.

1. Find the Windows Task Scheduler

Click into Administrative tools in the control panel

1.1 Click into Administrative tools in the control panel

Here it is. The elusive task scheduler (well not really... there are a bunch of ways to find it.)

1.2 Here it is. The elusive task scheduler (well not really… there are a bunch of ways to find it.)

 

2. Schedule a daily task to START Dropbox.exe at 12AM.

2.1 Click Create task to ummm, create a new schedule task.

2.1 Click Create task to ummm, create a new schedule task.

1. Name the Task. 2. Set to run whether the user is logged on or not.

2.2. Name the Task.
2.3  Set to run whether the user is logged on or not.

1. Click button to create a new trigger 2. Set New trigger Settings to "Daily" with a start time of 12:00AM since I want it to trigger on every morning at Midnight.

2.4  Click button to create a new trigger
2.5  Set New trigger Settings to “Daily” with a start time of 12:00 AM since I want it to trigger on every morning at Midnight.

1. Click button to create a new Action. 2. Browse to the program to launch (in this case for me its Dropbox.exe)

2.6  Click button to create a new Action.
2.7  Browse to the program to launch (in this case for me its Dropbox.exe)

3. Schedule a daily task to STOP Dropbox.exe at 5AM.

Since the scheduler only “Starts” programs, this requires us to write a tiny batch file that when started will kill Dropbox.exe.

Place the following

TASKKILL /F /IM "Dropbox.exe"

into a file named whatever your want .bat, in my case I called it ‘stopdropbox.bat’

Simple batch file to kill the Dropbox.exe process.

Simple batch file to kill the Dropbox.exe process.

Now lets just make another task schedule to Stop Dropbox.

Stop Drop Box Scheduled Task General Tab

Just like above, name this something and set it to run even when the user isn’t logged in.

Stop Drop Box Scheduled Task TriggerTab

Same as above except we are setting the trigger for 5AM, which for me is the end of the “FreeTime” window.

Stop Drop Box Scheduled Task ActionTab

As above, except here we are pointing to our little batch file that will kill the Dropbox.exe process.

Both Schedules set

Ahhh. Both tasks scheduled.

I hope this helps somebody out there.  If you wish Dropbox had some custom scheduling options built into their sync engine, or just appreciate the kludge I had to endure, please comment below.

Amazon Kindle 3

I bought the new Kindle 3 and I love everything about it.  Well, almost everything…

For some reason they went from the second generation Kindle’s innovative paging buttons, which used outside hinges to prevent accidental page changing, to the original style paging buttons.  This is very annoying and I find myself accidentally hitting the buttons at times. 

Other that that minor annoyance it is perfection.