Discussion

No hidden messages from eBay:
Criticism:
eBay not a good choice.
stegdetect does not find all images.

Analysing USENET images posted before Feburary 2001:
Using archives from the Internet Archive.

Stegdetect improvements:
JPEG headers contain comment and application markers.

JSteg, OutGuess and JPHide don't create any markers.

Treat JPEG files with comments or markers as negative.

Eliminates about 50% false positives.