Imaging through scattering media, for noble causes such as medical imaging, is a current and productive research area in optics. You can account for essentially arbitrary scattering as long as it doesn't change quickly. While the technology would be different, but I expect that the mathematics and the techniques already exist to thwart and such wall which you might design.
On the other hand, a 5mm sheet of aluminium ought to do the trick.
Three of the British warships sunk in the Falklands war
Physics World has a slightly more in-depth article.
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