How do the zip files after the first one uncompress in a file like 42.zip?

Question

I know this is a somewhat common question but none of the other posts had the answer I was looking for. To my understanding 42.zip contains many layers of zip files, but in my own testing, on mac, with a safer file, zip files inside of other zip files stay compressed when the surface file is uncompressed. Is the target expected to just uncompress all these files 1 by 1?

In: Technology

Answer 1

They are designed to work against programs that try to read the whole contents in one go, like if anti-virus software is trying to scan the whole file to detect viruses and so needs to keep uncompressing each layer to check for viruses.

This being a well-known exploit that is also relatively easy to defend against, I would be surprised if most common programs responsible for reading or unzipping files were not set up in a way that mitigates the potential for this to really do serious damage anymore.