Companies hoping to mitigate their exposure to insider attacks need to ensure they have good password, account and configuration management practices, as well as the right processes in place for disabling network access when employees are terminated.
Also crucial are the need to have formal processes for handling employee grievances and negative events in the workplace as well as for reporting suspicious behavior, according to a report released this week by the U.S. Secret Service and Carnegie Mellon University's CERT coordination center.
The report is based on an investigation of 49 cases of insider attacks via computer systems in critical infrastructure sectors between 1996 and 2002, In a majority of cases, the primary motivation for the attacks appears to have been revenge, said Matt Doherty, special agent in charge of the Secret Service's National Threat Assessment Center.
"In 92 percent of the cases, a negative work-related event triggered the insider action," he said.
The good news for companies is that most of the attacks were planned and not impulsive acts, which are "very hard to prevent" he said.
A key finding of the study was that a majority of the incidents involved former employees who shouldn't have been able to access the systems after they left the company they worked for, Doherty said.
The majority of the cases didn't involve sophisticated attack tools. Rather, they occurred because organizations "neglected to disable access upon termination," he said.
The study also highlighted the need for organizations to be particularly diligent when terminating systems administrators and other privileged users such as database administrators, said Dawn Cappelli, a senior member of the technical staff at CERT. A full 57 percent of the attacks were carried out by systems administrators, while 33 percent were caused by privileged users, she said.
"We found that because these users were technically sophisticated they were able to find the one gap that the organization missed," she said.
Many attacks involved the use of so-called logic bombs that were designed to corrupt data and delete files after a specified period of time. In one case, a logic bomb went off more than six months after the person involved had been terminated, she said.
"The most significant damage cost US$10 million in damages and resulted in the layoff of over 80 employees," she said. That attack involved a systems administrator at a defense manufacturing firm who deleted the only copy of the software supporting core manufacturing processes. The attack came in retribution for being terminated.
The key to mitigating exposure to such attacks is to know what to look for, Cappelli said. Good configuration management practices allow companies to identify unauthorized changes to software that could indicate the presence logic bombs, for instance, she said.
Similarly, the creation of unauthorized remote access accounts by systems administrators and other privileged users could be an indicator of trouble to come, she said.