Fill up your disk like bleachbit, but instead of using zeroes, actually fill the disk with file headers.

So someone running photorec or forensic recovery software gets a full disk.

Bonus points catalogue:

• zip/rar/7z bombs
• deleted dirs that have cyclical references
• real images that suck
  • valid data but too large to view
  • nested, overlapping files that are actually valid images
  • PNG files with RLE abuse to exhaust memory
• postscript data with recursion and infinite loops
• stick to utf8 where possible to fuck with string parsers
• file metadata sections that opens strings that never end
• use tricks from fuzzers to exhaust memory
• randomly generated so impossible to detect by signature alone
• take headers from real files that exist on the disk, but with bad contents

Related tool ideas:

• video / image encoders that embed headers into real data, so real files get filtered out
• file-level encryption that is trivially breakable, but costs about an hour of compute per file. So file recovery programs are annoyingly expensive, specially when combined with millions of dummy files.