OpenSSH in Apple Mac OS X 10.4.7 allows remote attackers to cause a denial of service or determine account existence by attempting to log in using an invalid user, which causes the server to hang.
https://exchange.xforce.ibmcloud.com/vulnerabilities/28147
http://www.vupen.com/english/advisories/2006/3101
http://www.us-cert.gov/cas/techalerts/TA06-214A.html
http://www.securityfocus.com/bid/19289
http://securitytracker.com/id?1016672
http://secunia.com/advisories/21253
http://lists.apple.com/archives/security-announce/2006//Aug/msg00000.html