Introduction
Canary Token is a great idea for early detection of possible intrusion in your system.
But be careful when you are using the free service from Thinkst Canary (https://canarytokens.org/generate) to generate Canary AWS tokens. You shouldn’t use it for real life production.
A threat actor may notice a common pattern in the AWS access key id (generated from Thinkst Canary) and avoid triggering your honeypot detection.
AWS Access Key ID Format
Aidan Steele wrote an in-depth article on AWS Access Key ID format. Highly recommend to read it.
Things to note from Aidan’s article:
- The first 4 chars of the AWS Access Key will be indicate the resource types (https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_identifiers.html#identifiers-unique-ids)
- The next 8 chars of the access key will be mapped to a specific AWS account.
We can get the AWS account id from the access key by using the aws-cli
$ aws sts get-access-key-info --access-key-id <<ACCESS_KEY_ID>> --query Account --no-cli-pager
xxxxxxxxxxxxxxxxxxxxxxxxxxxFlaws from the free service
Let’s generate a few Canary tokens from https://canarytokens.org/generate
[default]
aws_access_key_id = AKIAYVP4CIPPxxxxxxxU
aws_secret_access_key = xxxxxxxx
output = json
region = us-east-2[default]
aws_access_key_id = AKIAYVP4CIPPxxxxxxxW
aws_secret_access_key = xxxxxxxxx
output = json
region = us-east-2As you can see from the two generated Canary token, the four chars of the access key id show that this is an access key. Then the next crucial pattern (next 8 chars) will expose the information that this access key belongs to the AWS account from the free Canary token service.
A smart threat actor will detect this pattern and avoid using it. As a result, your Canary Token honeypot will likely to fail.
Takeaways
- Avoid using Canary Token services which provide predictable access key pattern. A threat actor can identify the pattern and avoid triggering the canary token.
- Canary Token is one of the detectors that we should use, but beware of confirmation biases (Canary token not triggered does not mean there is no intrusion).
