It is hard to not leak PII when redacting screen shots with some editor programs

I ran into a situation recently where I almost leaked some private data when using a sanitized screenshot. I took a screenshot of an order screen and then marked out all the PII. The programs retain the original image and editing information inside the image so that you can re-edit it later.  This means that anyone else can re-edit unless you protect yourself. 

I'm still not sure if I did a transitory upload into some cache before fixing this. 

TLDR 

Flatten or screenshot any editable PNG files. The latter works for every image.

Creating and Using the Image

This image started off as a Windows 10 snip screen capture. I then redacted the private information with black squares.  Later I came back and adjusted the squares to hide data.  I copied the image into a Powerpoint presentation and did a talk.  There was no risk up to this point.


My solution

I exported the Powerpoint as PNGi mage files.  The image files are flattened images of all the rendered components and are not editable PNG files.

Risky Behavior

Then I debated about posting the slide show as a PPT or taking the original image for a blog article like this one.  Both options would leak my home address and order number.
  1. The editable power point is, well, editable.  This means someone could edit the PowerPoint, copy the image and then edit the image with the original editor if they could guess which one it was.  The editing metadata might still be there.
  2. Putting the redacted image on the blog has the same risk.  Anyone could download the PNG from the blog and have a reasonable chance of editing the image and removing the redactions.

Options

  1. Export the image without any editability enabled.
  2. Take a screenshot of the image after editing it.
  3. Flatten the image using the editing tool.

Revision History

Created 2023 02

Comments

Post a Comment

Popular posts from this blog

Installing the RNDIS driver on Windows 11 to use USB Raspberry Pi as network attached

Image
I do a lot of my development and configuration via ssh into my Raspberry Pi Zero over the RNDIS connection. Some models of the Raspberry PIs can be configured with  gadget drivers  that let the Raspberry pi emulate different devices when plugged into computers via USB. My favorite gadget  is the network profile that makes a Raspberry Pi look like an RNDIS-attached network device.  All types of network services travel over an RNDIS device without knowing it is a USB hardware connection. A Raspberry Pi shows up as a Remote NDIS (RNDIS) device when you plug the Pi into a PC or Mac via a USB cable. The gadget  in the Windows Device Manager picture shows this RNDIS Gadget connectivity between a Windows machine and a Raspberry Pi. The Problem Windows 11 and Windows 10 no longer auto-installs the RNDIS driver that makes magic happen. Windows recognizes that the Raspberry Pi is some type of generic USB COM device. Manually running W indows Update  or  Upd...
Read more

Understanding your WSL2 RAM and swap - Changing the default 50%-25%

Image
The Windows Subsystem for Linux operates as a virtual machine that can dynamically grow the amount of RAM to a maximum set at startup time.  Microsoft sets a default maximum RAM available to 50% of the physical memory and a swap-space that is 1/4 of the maximum WSL RAM.  You can scale those numbers up or down to allocate more or less RAM to the Linux instance. The first drawing shows the default WSL memory and swap space sizing. The images below show a developer machine that is running a dev environment in WSL2 and Docker Desktop.  Docker Desktop has two of its own WSL modules that need to be accounted for.  You can see that the memory would actually be oversubscribed, 3 x 50% if every VM used its maximum memory.  The actual amount of memory used is significantly smaller allowing every piece to fit. Click to Enlarge The second drawing shows the memory allocation on my 64GB laptop. WSL Linux defaul...
Read more

Almost PaaS Document Parsing with Tika and AWS Elastic Beanstalk

Image
The Apache Tika project provides a  library capable of parsing and extracting data and meta data from over 1000 file types.  Tika is available as a single jar file that can be included inside applications or as a deployable jar file that runs Tika as a standalone service. This blog describes deploying the Tika jar as an auto-scale service in Amazon AWS Elastic Beanstalk.  I selected Elastic Beanstalk because it supports jar based deployments without any real Infrastructure configuration. Elastic Beanstalk auto-scale should take care of scaling up and down for for the number of requests you get. Tika parses documents and extracts their text completely in memory. Tika was deployed for this blog using EC2 t2.micro instances available in the AWS free tier. t2.micro VMs are 1GB which means that you are restricted in document complexity and size. You would size your instances appropriately for your largest documents.   Preconditions An AWS account. AWS ac...
Read more