File pumping is a technique used by malware and ransomware that is used to artificially inflate the size of a file by injecting it with additional bytes to bypass cybersecurity tools. This technique can work because many cybersecurity tools have a feature to bypass file scanning of files beyond 100MB.

This technique is often used to modify legitimate applications with “pumped” variants and then replace the original on public servers. This modified edition is then used as a mule to distribute the malware and infect the victims device.