The most well-known file matching this description is . It is a tiny 42,374-byte (approx. 42 KB) zip file that, when fully unzipped, expands to 4.5 petabytes of data.

If you are looking for a "good write-up" on how these work technically, these sources are highly regarded:

: It consists of 5 levels of nested zip files. The bottom level contains 16 files, each being 4.3 GB of zeros, which compress incredibly well.

: For a visual breakdown of the math, searching for "Zip Bomb explained" on YouTube often leads to excellent technical summaries by channels like Computerphile .

: This is the definitive modern write-up. Fifield explains how to create a "non-recursive" zip bomb that achieves high compression ratios without nesting files, making it much more dangerous for scanners. You can find his full research and graphs on his personal site .

It sounds like you're looking for the famous "44.5 KB" zip bomb (often rounded to 45K or 44K) and its technical write-up.