I will hack your systems with an SD Card

Pierluigi Paganini January 01, 2014

The hardware hacker Bunnie Huang presented at the Chaos Compute Club Congress how to exploit SD cards microcontrolled for malicious purposes.

How is it possible to exploit SD Card, USB stick and other mobile devices for hacking? Another interesting hack was presented at the Chaos Computer Congress (30C3), in Hamburg, Germany, while yesterday I’ve published a post on an hack against ATMs via infected USB sticks, today I’m writing on the hacking of SD Card flash storage.

The researchers demonstrated how to hack the microcontroller inside every SD and microSD flash cards to realize a man in the middle attack.

SD cards contain powerful micro controllers that are exploitable by hackers to make them insecure.

The hacker Bunnie Huang described the procedure to do it and published also a post on the topic, it seems that to reduce SD cards price and increase their storage capability, engineers have to consider a form of internal entropy that could affect data integrity on every Flash drive.

SD card hack

Almost every NAND flash memory is affected by defects and presents problems like electron leakage between adjacent cells.

“Flash memory is really cheap. So cheap, in fact, that it’s too good to be true. In reality, all flash memory is riddled with defects — without exception. The illusion of a contiguous, reliable storage media is crafted through sophisticated error correction and bad block management functions. This is the result of a constant arms race between the engineers and mother nature; with every fabrication process shrink, memory becomes cheaper but more unreliable. Likewise, with every generation, the engineers come up with more sophisticated and complicated algorithms to compensate for mother nature’s propensity for entropy and randomness at the atomic scale.” wrote Huang.

A hacker could exploit the firmware loading mechanism, usually used only at the factory, to load  malicious code, a techniques largely adopted by counterfeiters who create SD cards that report a larger capacity than they have.

The firmware on the SD cards can be updated, but according Huang’s revelations most manufacturers leave this update functionality unsecured.

The hacker during the presentation at 30C3 reverse-engineered the instruction set of a particular microcontroller to inspect firmware loading mechanism.

The attackers suitably modifying the firmware could hack any device that uses the compromised SD card (e.g. A mobile device, Wi-Fi equipped camera), the flash memory will appear to be operating normally while hacking the hosting equipment.

The SD card could make a copy of the contents in a hidden memory area or it could run malicious code while idle avoiding detection mechanisms.

When we speak about USB hacking or SD Card hacking we must consider that we are approaching the hacking on a large-scale due the wide diffusion of these components. Microcontrollers cost as little as 15¢ each in quantity, they are everywhere and every device that use them could be hacked.

Another consideration that must be done is that Governments and high profile hackers could be very interested in this type of attack for both cyber espionage and sabotage purposes, arrange a countermeasure against these types of threat it is very hard.


A curiosity for the “hackers inside” …  these cards could be reprogrammed to become Arduino open source microcontroller and memory systems.

“An Arduino, with its 8-bit 16 MHz microcontroller, will set you back around $20. A microSD card with several gigabytes of memory and a microcontroller with several times the performance could be purchased for a fraction of the price,” he writes.

Look closely at the presentation … and distrustful of SD cards from now on.

Pierluigi Paganini

(Security Affairs –  SD card, hacking)

you might also like

leave a comment