The security firm looked at 48 entertainment and media firms running its sensors during a six-month real-world test phase between January and June 2014, finding that 91 percent were believed to have suffered some kind of breach caused by a failure in conventional defences.
The notion of a 'breach' is ambiguous in this context but it was presumably one or more security events not picked up by the network's firewalls, intrusion prevention systems (IPS), gateways or anti-virus defences, later noticed by FireEye's sensors.
While bad, that figure was actually a small improvement on the 98 percent breach figure FireEye reported from an earlier 2013 study. FireEye also detected 'advanced malware' was now being used in nearly a fifth of security breaches.
Other sectors covering the 1,214 US firms studied were even worse, with retail, Agriculture, Auto/Transportation, Education, and Healthcare/Pharmaceutical industries suffering breaches in 100 percent of networks during the period. Legal and Federal Government/State Government recording a 95 percent figure, services 94 percent, and high-tech 97 percent.
Only Aerospace/Defense did relatively well, achieving a still-high breach score of 76 percent.
FireEye's report ridicules the dependence firms have on traditional security layers as a 'Maginot Line', a reference to the supposedly impregnable French defences Hitler's armies simply bypassed at the start of WW2.
"As we have seen over the last year, when just one advanced attack slips past the existing defenses of companies, it can have both a costly and debilitating impact that takes months to repair," said FireEye CEO, Dave DeWalt.
"The results of our Maginot studies clearly show that there are gaps in the way many global businesses are secured, opening the door for aggressive threat actors to conduct anything from state-sponsored espionage to cybercrime."
Despite the compelling force of FireEye's analysis and the message that non-integrated defences no long stop attacks, the view they produce suits the firm's marketing of its own anti-APT security technology. Without more data on the severity of the breaches detected by its sensors it's also hard to judge the cost-benefit analysis for investment in newer technology.
What is not in doubt is the volume of attacks now being thrown against defences, as a FireEye study looking at Europe from last October underlined. Indeed, many of the popular remote access Trojans detected during that study were the same tools noticed during the latest study of US sectors.