Hak5 1722 – WiFi Deauth Attacks, Downloading YouTube, Quadcopters and Capacitors
WiFi Deauth attacks using the new WiFi Pineapple firmwares Recon Mode, downloading YouTube videos from the command line, quadcopters on a boat, and capacitors. All that and more, this time on Hak5!
Downloading from YouTube
Youtube-dl is amazing. I’m completely switched over from all of the other Firefox plugins and other hacks. Best of all, it’s open source and command line driven – meaning it can be used as part of scripts to systematically download videos from YouTube. It also supports a plethora of other video sites. I really can’t speak of it highly enough. Check it out at http://rg3.github.io/youtube-dl/.
What is a Capacitor?
Two-Terminal electrical component. Can store energy, instead of limiting it or emitting it. Used to suppress voltage spikes, signal filtering, and local energy storage.
On schematic… – Should have name and capacitance # (i.e. how many farads).
Farad tells you how much charge it can store. More capacitance = more capacity to store a charge. 1 Farad is a lot of capacitance. Usually = picofarad (10 to the 12th) or microfarad (10 to the 6th)
How is it made? – Two metal plates with dielectric insulation stuff in middle. Plates far away from each other = less capacitance. Plates close together = higher capacitance.
The reason why it works the way it does is because of those super fun electrons. Negative electrons get sucked into the capacitor through one side and get ‘stuck’ on the metal frame. The positive ones end up on the other plate. The positive and negative electrons are attracted to each other and end up in this forever dance cycle because they can’t get past that dielectric stuff in the middle. This creates storage of energy.
Eventually the capacitor won’t be able to hold anymore of those negative electrons on one of the plates, so it starts kicking out others who want to join, sorta like an elite club that only allows so-many people in.
The farads will tell you the max amount of electrons that capacitor can hold.
MATH! Q=CV means Q (charge currently being stored) = C (Capacitance in farads) * V (voltage between it’s plates). Farads is known. More voltage = more charge and vice versa. If I have a 1 farad capacitor, and 2 volts, I can store 2 coulombs of energy per 2 volts. The amount of current through the cap depends on the capacitance and how fast the voltage rises or falls. If the voltage is high, the current will be high. A slower rising voltage = a slower current. If the voltage is unchanging, the current is unchanging, nothing happens. I don’t want to bore you to death with calculating current thru a cap, so we’ll skip that until we get into more in depth builds.
What do they look like?
Keep in mind: More capacitance = a larger cap. If you exceed the max volt, you can pop a cap. Caps will leak stored energy over time, but slowly. Usually have 0.01 or less resistance called the equivalent series resistance. Tolerance (or the capacitance rating) might be off from + or – 1% up to 20%.
Ceramic capacitors are orange, small, and have low capacitance. Come in sizes less than 10 microfarads. They are also very cheap!
Electrolytic caps are cylindrical, range from 1 microfarad up to 1 millifarads, and store lots more capacitance in a small size. They are also polarized, so make sure you plug them in the right way or they POP! Anode must be at higher voltage than cathode, but they have short and long legs or are marked with + and -. Also problem with leakage in these.
Supercapacitors store huge amounts of charge but can’t deal with lots of voltage. They are small and blue (sometimes)
Others also, but we won’t go into those.
If you put sev. caps in a parallel design, the total capacitance of that board will be the sum of all caps.
Caps in a series is weird though. The total capacitance of caps in a series is the inverse of their sum of all inverse capacitances. So if I have 2 10farad supercaps, they would normally equal 20. But you’d take c1*c2 and divide by their added total of 20. 10*10 = 100 / 20 = 5 farads.”