Rogue devices are intrusions on networks that are implemented either internally or externally without permission from network administrators. The only way to ensure a network's security is to perform audits and threat analyses in threat environments, said Morgan.

Laura Chappell, IT security expert and FBI consultant, said default settings, which include usernames and passwords, are easily found on the Internet.

"From here, a hacker can simply go in and gain access to your corporate network," she said.

Nearly 30 percent of companies made no attempt to protect their business information at all with no encryption keys used to access the wireless network. "This means that clear-text communications over the wireless network can easily be intercepted and read," Chappell said.

"Adelaide's CBD-based companies are the biggest offenders at 36 percent. This figure is extremely high. If confidential information is crossing the wireless network in plain text, then that's handing corporate secrets to the competition on a platter."