[Van Eck phreaking](https://en.wikipedia.org/wiki/Van_Eck_phreaking)
Use autocorrelation of signal to determine the time it takes to process each row of pixels, and use this to plot the normalized signal intensity in a rectangular grid, which reconstructs the original monitor display.
[Full writeup](https://github.com/the-entire-country-of-ireland/ctf_writeups/blob/main/UnionCTF_2021/seeing-through-walls/solve_walls.ipynb)