Solaris 9, with Solaris Auditing enabled and certain patches for sshd installed, can generate audit records with an audit-ID of 0 even when the user logging into ssh is not root, which makes it easier for attackers to avoid detection and can make it more difficult to conduct forensics activities.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5282
https://exchange.xforce.ibmcloud.com/vulnerabilities/39185
http://sunsolve.sun.com/search/document.do?assetkey=1-66-201310-1
http://sunsolve.sun.com/search/document.do?assetkey=1-26-103172-1