One night, her phone buzzed at 3:00 AM. It wasn't the usual “transfer complete” alert. It was .

Marta’s heart raced. She pulled up the FileCatalyst transfer logs. The file had arrived on time. But Tripwire showed that 14 minutes after FileCatalyst reported a successful checksum, the file had mysteriously been overwritten.

She cross-referenced the timestamps. FileCatalyst said: "File delivered intact. SHA-256: 7A8F... valid." Tripwire said: "File altered at 02:14:33. New hash matches 'test_pattern_old.dat'."

It didn't make sense. A classic man-in-the-middle would have been caught immediately. But this was a delayed mutation.