Check the SSH client configuration for allowed ciphers. Note that keywords are case-insensitive and arguments (args) are case-sensitive.
keyword=Ciphers
arg(s)=<comma separated cipher(s)>
Default values include: "aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc,arcfour,arcfour128,arcfour256blowfish-cbc,cast128-cbc".
For this check, the only allowed keyword values are those from the above list with the "aes" prefix and the "-ctr" suffix.
Note: When the default "arg" value exactly matches the required "arg" value (see above), the <keyword=arg> entry is not required to exist (commented or uncommented) in the ssh (client) or sshd (server) configuration file. While not required, it is recommended that the configuration file(s) be populated with all keywords and assigned arg values as a means to explicitly document the ssh(d) binary's expected behavior.
Examine the file.
# cat /opt/ssh/etc/ssh_config | tr '\011' ' ' | tr -s ' ' | sed -e 's/^[ \t]*//' | grep -v '^#' | grep -i "ciphers"
If the returned ciphers list contains any cipher other than those with the "aes" prefix and the "-ctr" suffix, this is a finding.