SSH private keys: How do threat actors find exposed keys?

Cybersecurity vendor Wordfence recently reported that it detected a spike in scanning for SSH private keys. How can threat actors find these keys? What should enterprises do to protect them?

When people, including me, are in a hurry, they often take shortcuts or don't look closely at specific details. While it's impossible to know all of the ways that something can be abused -- especially when dealing with something you might not fully understand -- you might make mistakes.

One instance where this might happen is when a web developer uploads software to a new server and accidentally includes and exposes his or her SSH keys to the internet. While the exposure of SSH keys is usually an accident, attackers have figured out how to scan for them.

Wordfence recently released a blog about this type of incident and how they have seen an increase in scanning. Threat actors can find SSH keys the same way that everyone else finds information on the internet -- by using a search engine.

An example of this includes the following search in Google: "filetype:key"-----BEGIN RSA PRIVATE KEY-----"site:<WEBSITENAME>" where <WEBSITENAME> is replaced with a specific website name in order to find any SSH private keys uploaded to that website. This search can be modified to be more open-ended or even customized to search the content on your website. The file system of a server can be searched to identify any SSH private keys and make sure any permissions are set correctly.

Enterprises should educate their IT staff to protect their SSH private keys with methods such as password usage, the removal of any public access to SSH private keys and ensuring that they are securely using SSH. Likewise, Wordfence has their own scanner that will scan for SSH private keys on a website.

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