We are using BM3.8SP? and SurfControl.

All of the computers on the network are using the proxy and being blocked
from denied sites by SurfControl. A student brought in their Macintosh
laptop today and they were able to access anything on the internet without
logging into the network at all. They had an IP address through DHCP and
the proxy address was in their browser. What would cause them to be able to
bypass any SurfControl blocking?