What is a "canary in a coal mine"
“Canary in a coal mine” means an early warning sign of danger—especially one that signals hidden or emerging threats before they become obvious.
Historically, coal miners used actual canaries as safety monitors deep underground. These birds are highly sensitive to toxic gases like carbon monoxide and methane, which are colorless and odorless. If a canary became ill or died, it warned miners that the air was unsafe, giving them time to evacuate before the gases reached lethal levels.
Years back, our friends at Huntress introduced canary files: serialized, random files placed in key folders on a workstation's local drive. The premise was that it would get swept up in any mass data exfiltration. When clicked, it would phone home to Huntress to alert that it had been touched and was potentially sitting on the internet.
Cool stuff.
I always wanted Huntress to allow their canary files to be placed on critical share folders, but they never added that feature.
Today, I was listening to a presentation from a SOC vendor who wanted everyone to know that "they loved canaries" and would love to know what canaries their clients had deployed.
The concept of canary files has indeed evolved to precisely what I have wanted. There are free or very inexpensive canary files you can create and drop into high-value folders on your network and cloud infrastructure. They are just random serialized files that can phone home if touched.
Sprinkle them into your shares with sensitive data. Then, if someone moves, opens, or exfiltrates parts of your sensitive data, the canary file should act as a beacon to notify you that something bad is happening.
If you are not actively watching your firewall or logs, this is a no-brainer to give you visibility into your data being moved. If you are one of those sites with a less robust EDR endpoint solution that covers less than 100% of your endpoints, this a way know data is leaving through your blind spot.
And if you are doing everything correctly, this is a simple way to have a separate security layer that independently verifies that your data isn't leaving your network for little to no cost.
It is a win-win situation, no matter your situation.
Put implementing strategic canary files on your list of security improvements as we move through the Fall and Winter.
If you need help implementing a Canary file strategy on your network, please reach out to us. Acture is happy to assist you in getting this setup.