It turns out there's a significant flaw in the approach. Because both the medallion and hack numbers are structured in predictable patterns, it was trivial to run all possible iterations through the same MD5 algorithm and then compare the output to the data contained in the 20GB file. Software developer Vijay Pandurangan did just that, and in less than two hours he had completely de-anonymized all 173 million entries.
According to chat logs recorded by Monsegur at the behest of the FBI and obtained by Motherboard, the informant directed hackers to pilfer as much data as possible from ManTech's servers as investigators stood by. Stolen data was published as the third installment of AntiSec's ... collection of leaks intended to embarrass the same federal agency that presided over the hack and others.