As per the same question that was directed on the meta: X company has requested a scan of my passport
Handling various security documents frequently, these are some of the pointers I give to people:
- Most security features don't appear in a scanned image
- Send the scan in black in white
- Send a lower resolution, or compressed image (Medium/Low JPEG)
- Attach only one side of the document if possible
- Ask the company what their data retention policies are
- Get a bank or other notary public to notarize the scanned copies
- Do a search to see if there are any past data leaks at the company (e.g. Yahoo)
- See if you can arrange for a physical presentation of the document.
- Send the document with a link to a service that allows for retraction (Expiry)
- Ask about sending the images by Fax
- Ask if they require document numbers only (much more secure)
- If you are still concerned, apply a physical/digital watermark
By not verifying an identity document in person can land companies in hot water, and is simply bad practice. There is no valid excuse why one would not verify the true holder of the document, or if there is in fact a true document at all. Companies are unfortunately lazy in this regard.
There are plenty of scans of common documents on the internet, which include US/Canadian/UK passports and drivers licences. Many come as Photoshop templates with instructions on how to paste your own image in, change a few other personal features (name/date of birth), and how to attempt to pass it off as a real scan.
Once you have sent an image (or series of images) off, there is very little you can do to protect yourself. There is a whole area of study related to Data Loss Prevention when it comes to company secrets. Most of these can not be applied to the "Average Joe", as it requires an elaborate setup.
By refusing to send a scan of a document makes it look as if you are hiding something, which may or may not be true. When applying for a job, refusing to send identity documents by email could result in the loss of an opportunity. So unfortunately, you are between a rock and a hard place when it comes to this.