The Hacker Factor Blog

The hardest parts of forensic analysis isn't the tools; it's the training. Anyone can buy rubber gloves, swabs for collecting blood samples, and plastic evidence bags. But if you are not trained to properly collect, handle, and evaluate evidence, then the tools and methods are meaningless.

The learning curve is the hardest part. To address this, I've been working on documentation and worksheets for digital image analysis and photo forensics. While there is still a steep learning curve, the investigator can review the worksheets as a checklist for common things to evaluate. The associated documentation provides details regarding the checklist items, in case the investigator needs to review how a particular system works.

An Eye For Details

While luminance gradient and error level analysis draw pretty pictures, the most important tool is basic observation. It is one thing to see the big and obvious signs of manipulation. It is something else to remember all of the fine details.

The folks at Photoshop Disasters recently posted a couple of amazingly bad shopped pictures that clearly illustrate the power of observation for detecting image modifications.

The first picture comes from an ad campaign for fingernail polish. The picture is supposed to show a model and some nail polish. The magical stars that go from her elbow to the picture frame are just artistic. However, it is the fine details that make this such an obvious disaster... Just using your eyes, what stands out as abnormal and not intentionally artistic? Give yourself a minute to look over it, then scroll down and see how many things you noticed.



If you only saw the disconnected leg, then give yourself one point. (If you didn't notice the leg, then go back and try again. As Thall commented at PsD, "That women could birth a horse or two with those hips!") Other oddities include:

• Her waist is out of proportion.
  
• There is a black triangle between her torso and floating leg. The artist forgot to cut out this area.
  
• Her left forearm (photo right) is significantly longer than her right forearm.
  
• She has two thumbs on her lower hand. (One thumb could be her foot showing through a strap in the shoe, but it is actually blended into the hand.) Oh, and don't mind the "S" on her finger; other photos show it as a tattoo or something.
  
• Her neck is showing a tendon, indicating that her head is turned. However, her head is looking straight and is not centered on the neck. Yes, they cut off her head and pasted on a different head.
  
• She is missing a clavicle (shoulder bone) -- one is there, but the other was erased.
  
• Her boobs are different sizes, and not in a natural way (unless the left one is half as long and deflated...).
  
• The shadow under her head indicates a bright light to the upper right. But the floating leg isn't casting the same shadow onto the other leg. And the shadow from the sleeve onto her straight arm has a shadow going the other direction. Inconsistent lighting means splices.
  
• Of course, all of these are issues with the woman. Over at PsD, ZaphodQB noticed that the reflection of the black polish does not meet the bottom of the black bottle.

This isn't the full list. What else do you see? No wonder their product is called "Oops!"

The Perfect Model

I'm always looking for good sample images that demonstrate specific points. Ideally, I want one picture that only demonstrates one thing, then another that demonstrates the same thing with more complexity, and finally an example that brings everything together.

From the Oops! example, we know to look for different classes of manipulation. These attributes become our checklist:

• Limbs: Are all of them accounted for? Are all connected? Are they the right proportions?
  
• Reflections: Do items line up properly?
  
• Shadows and lighting: Are they consistent?

Now we can apply this to a new set of pictures.

At Photoshop Disasters, they featured a picture from the French fashion house, Louis Vuitton. However, the web page at Fashion Gone Rogue contains many pictures from the "Louis Vuitton Fall 2010 Campaign" (also available at Fashionologie). It is an homage to digital distortions.

Starting at the top is the banner for Fashion Gone Rogue. Her upper arms are very different lengths. It is also faint (better seen with luminance gradient), but it looks like there is a strap or something going across her shoulder and down her cleavage. (This could be where the artist stopped altering the skin.)

Mirror Mirror On The Wall

The various photos from Louis Vuitton have been equally mangled. Let's use our new checklist...

The picture claims to show three women in a dressing room. Each has different color hair: red, blonde, and brunette.

Limbs
Every person has two arms? Check! Extra fingers? Nope. Legs and feet? Uh... the brunette on the right has an ankle but is missing toes.

Reflections
The right-most mirror (behind the toe-less brunette) is not reflecting anyone in the room. The blonde has her hand up in the room but her hand is down in the mirror. That same mirror also shows a light bulb in the reflection, but the bulb does not exist in the room.

The second mirror from the right shows bulbs but they don't align with the bulbs in the room.

The mirror on the far left shows red's head from the back. However, red's head is not turned to show her back to that mirror. And the mirror's reflection shows the lamp on the wrong side. The reflection does not match the room.

Lights and Shadows
When an item sits next to a illuminated light, it is made brighter. And when items are facing away from the light, they are in shadow. Complex lighting, such as floods, reflectors, and bright ambient lighting, can mitigate shadows.

However, those mirrors have a lot of bright lights. The women should have brightly lit backs. But this isn't what we're seeing. The brunette has bright reflections off her chest but not her back. The blonde has a bright clavicle but an under-lit neck. The pile of junk in the back has a brown fabric thing above the handbag; it is lying next to a light bulb and not lit up.

This isn't a comprehensive list and there are other oddities that are not in our checklist. For example, the blonde's dress seems to have a layering issue with red's chair. The dress fabric suddenly becomes semi-transparent and you can see the chair through it.

Frankly, I kind of doubt that these three women even posed together for this picture.

Some of the pictures in this series are much worse than others...


Dear Louis: While fabrics may be diaphanous, people are not. And while models may be vamps, they are not vampires. Please fix the left mirrors. You know, the ones with the time-delay reflections that show the brunette in two alternate positions and don't reflect the blonde.

Dress For Success

While I can criticize these ads for pasting in people, changing reflections, and digitally altering lighting, I have to give Vuitton one piece of credit:

Beyond expected color enhancements (applied to the entire picture) and spicing blends (expected from a composite image), I have not detected any modifications to the clothing. Well done. Unlike Ralph Lauren and Victoria's Secret, Vuitton's pictures do not appear to be a product bait-and-switch.