Some of this data is old and includes employees that are no longer working for us. Doesn’t this mean we are not at risk?

While employees may have moved on from your organization, their company issued credentials can still be active and valid within the 3rd party systems they used while employed. In many cases, the 3rd party systems or databases that have been compromised have been in existence for 10+ years holding millions of “zombie” accounts that can be used to exploit an organization. Discovery of credentials from legacy employees should be a good reminder to confirm you’ve shut down any active internal and 3rd party accounts that could be used for exploit.