A company believes that one of its employees is leaking sensitive data and calls in

ThreatSpike to help. With ThreatSpike$$s help the company gives out a file to each

employee. Within $24$ hours is notified that a copy has been found on a file sharing

website. There is no record of who uploaded the file, the SHA$256$ hash of all the files

handed out are identical, the names appear the same but ThreatSpike on

downloading a copy of the leaked file can still work out who leaked it$.$ How?