A system reports credentials on nodes of a network. Nodes are assigned to security silos. If a credential reported from a node is found to match a credential found on a node outside of its security silo or be for authentication with a node outside the its security an alert is generated, unless proper precautions are generated. Credentials may be reported as one-way hashes of credentials. Security silos may be automatically generated to segregate at-risk nodes from critical servers based on the presence or use of email clients and browsers. Precautions that may be used to suppress alerts, such as using KERBEROS TGT.