How do I secure /tmp and /var/tmp on a OpenVZ VPS?

Secure /tmp

Edit /etc/fstab by typing the command
nano -w /etc/fstab
Paste the following at the bottom of /etc/stab that you just opened:

none /tmp tmpfs nodev,nosuid,noexec 0 0

Press ctrl + x to close the file, press y to save it.
Remount /tmp by typing the following then press enter:
mount -o remount /tmp

You can verify that /tmp is correctly mounted by typing df -h and you should see something similar to the following: none          3.9G   0  3.9MG   0% /tmp.

Secure /var/tmp

Backup /var/tmp by typing the following:
mv /var/tmp /var/tmpbackup
Make a symbolic link that makes /var/tmp point to /tmp by typing the following:
ln -s /tmp /var/tmp
Copy back the old data using the command:
cp /var/tmpbackup/* /tmp/
Remove the un-needed backup you created:
rm -rf /var/tmpbackup

You should now reboot your VPS. This means /tmp and /var/tmp are now secured.