Large numbers of data breaches are being initiated by targeted malware that antivirus software simply can't detect, an analysis of 300 real-world incidents from 2011 has suggested.Trustwave's 2012 Global Security Report studied 300 incidents across 18 countries where the company's SpiderLabs division was called into investigate what had gone wrong.In 100 percent of the incidents, malware undetectable by a representative sample of antivirus products must have been the root cause of what had happened, typically entering an organisation via an employee's PC.Specifically, 88 percent of the malware isolated by Trustwave was able to evade detection by all antivirus products used in the test, while the remaining 12 percent that did flag malware were only able to do so retrospectively, possibly months after being used in an attack.In other words, the malware had won the battle on every occasion. "We have anti-virus, shouldn't we be protected?" is often heard during Trustwave investigations," the report found. "The historical perception of antivirus and the sometimes blind faith in its ability to detect and stop malware is one of the reasons attackers are so successful in what they do."The net effect of this invisibility was that 84 percent of the affected organisations only realised they had suffered a data breach when alerted by an external body such as law enforcement, a regulatory body, a partner or even the public. By that time, the breach had been active on the network for a startling average of 173 days, with some appearing to go back years."Antivirus has a role but many organisations make that a large role," said Trustwave SpiderLabs head, Nicholas J. Percoco. "The reality is that antivirus vendors only know about what they know about.""The criminals go to great lengths to develop new malware that they do not throw out," said Percoco. Antivirus software couldn't detect it because its targeted nature meant that vendors might never see it until it had been used in a successful attack.A common factor in three quarters of the breaches was that some aspect of the IT had been outsourced to a third party, he said.The most commonly stolen data were customer records, responsible for 89 percent of lost data, with more than a third of the detected breaches happening in franchised businesses. The food and beverage industry accounted for 44 percent of breach incidents.In addition to an over-reliance on antivirus, the commonest security weaknesses included poor or non-existent logging and passwords being shared between systems; the favourite password found was 'password1'. Trustwave also found a decided lack of enthusiasm for data breach disclosure.