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.
: 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. Download 445K zip
: Do not attempt to decompress this file on a standard computer. Most modern antivirus programs and zip utilities will detect it as a "zip bomb" or "decompression bomb" and block it to prevent your system from crashing or running out of disk space. Recommended Write-ups The most well-known file matching this description is
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
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.
: For a visual breakdown of the math, searching for "Zip Bomb explained" on YouTube often leads to excellent technical summaries by channels like Computerphile .