"I don't beat them up for it," said Jason Healey of the Atlantic Council and a former White House and Goldman Sachs security official. "Experts have long had trouble agreeing on estimates that are within even two orders of magnitude of each other."
Healey said the damage estimates of the first large-scale cyber incident, the Morris worm of 1988, "ranged from $200 to more than $53,000 per installation, while the most widely cited estimate of the total damage ranged from $100,000 to $10 million: two full orders of magnitude. And that was 24 years ago."
Gary McGraw, CTO of Cigital, said he suspects McAfee "followed protocol [in its report] up to the end, where they did some crazy math -- I think control got turned over to the marketing guys."
But he admits, "I've cited that [$1 trillion] number in my own work. I was writing a piece about cyberwar for a think tank. I was trying to make a point about cybercrime being worse than cyberwar -- which the risks of cyberwar were exaggerated, and cybercrime was worse. How's that for irony?"
There are other reasons that estimates are difficult. In a recent paper called "Measuring the Cost of Cyber Crime," done for the U.K. Ministry of Defense, the authors listed a chart that suggested the annual cost of worldwide cybercrime was about $225 billion -- less than 25 percent of the McAfee estimate.
But the authors included a host of caveats, including: "There are over 100 sources of data on cybercrime, yet the available statistics are still insufficient and fragmented; they suffer from under- and over-reporting, depending on who collected them, and the errors may be both intentional (e.g., vendors and security agencies playing up threats) and unintentional (e.g., response effects or sampling bias)."
They also note that there are differences between direct and indirect costs. Indeed, the group even refuses to add up its own figures to report a total, noting that "many of these are extremely rough estimates -- we believe it is entirely misleading to provide totals lest they be quoted out of context, without all the caveats and cautions that we have provided."
In short, they are much more cautious than either McAfee or Symantec.
But the other reason some experts are willing to grant those companies some leeway is because, whatever the precise number is, it is a very big one. Indeed, there are daily stories about data breaches -- the recent hack of Dropbox that resulted in the theft of user names and passwords is just one of the more recent.
NetBenefit reported research by software vendor SecurityCoverage that found the number of pieces of information illegally sold during the first quarter of 2012 was up 67 percent from 2010 figures.
"It's not good to inflate estimates," Gary McGraw said. "But cybercrime is a huge problem. You can talk about cyberespionage and cyberwar, but cybercrime is worse than those."
The solution is to "build stuff right," he said. "If we did that, it would reduce the probability of war, cut down on espionage and take a bite out of crime."
Read more about malware/cybercrime in CSOonline's Malware/Cybercrime section.