http://www.redhat.com/security/data/openssh-blacklist.html - RedHats distribution servers were infiltrated and some openssh packages were compromised. There is a small possibility that some RHEL4 and RHEL5 systems who updated during the compromise have installed malicious openssh packages. RedHat has released a script to determine if the system has been compromised. It is suggested that the script (available at the URL above) be run on all RHEL4 and RHEL5 machines to determine compromise. Please contact me immediately if any of your machines turn up with a compromised package.