Some Person was login to your Linux VM? You have more than 10 people with a login to the System. In var/log/auth.log(Ubuntu) you see a fingerprint from ssh key.

cat ~/.ssh/authorized_keys | xargs -n1 -I% bash -c ‘ssh-keygen -l -f /dev/stdin <<<“%”‘

2048 32:3s:32:91:a2:f5:1c:3c:25:6e:05:f2:25:24:5b:01  person1@example.com (RSA)
4096 32:3s:32:91:a2:f5:1c:3c:25:6e:05:f2:25:24:5b:02 person2@example.com (DSA)
2048 32:3s:32:91:a2:f5:1c:3c:25:6e:05:f2:25:24:5b:03 person3@example.com (RSA)
4096 32:3s:32:91:a2:f5:1c:3c:25:6e:05:f2:25:24:5b:04 person4@example.com (RSA

Now you become a list with all Fingerprints and Name of your login users.

Find it out which person have login to your system….

grep “32:3s:32:91:a2:f5:1c:3c:25:6e:05:f2:25:24:5b:03” /var/log/auth.log

Some Code Snipes found here

http://serverfault.com/questions/413231/how-to-get-all-fingerprints-for-ssh-authorized-keys2-file