About 58 percent of cyber incidents reported in the public sector were caused by government employees, according to an annual data breach report compiled by Verizon. The findings -- stripped of identifying information -- do not mention ex-contractor Edward Snowden's mammoth leak of national secrets.

Even if Snowden's leaks had been included in the tally of results attributed to insider threats, they wouldn't have made much of a dent.

"If that were recorded in here, that would be a single event," said Jay Jacobs, a Verizon senior analyst and co-author of the report.

Most (34 percent) of the insider incidents in the global public sector during the past three years were miscellaneous errors such as emailing documents to the wrong person. Unapproved or malicious use of data by public servants accounted for 24 percent of reported incidents.

Surprisingly, cyberspying and intrusions via security holes in websites, known to be big problems in government, represented less than 1 percent of the situations reported.

The off-kilter numbers in government reflect mandatory reporting requirements for mundane incidents, Jacobs said. Small data leaks that happen every day overshadow frequent, but not daily, hacks.

By contrast, cyber espionage accounted for 30 percent and 40 percent of incidents in the manufacturing and mining industries, respectively. And 41 percent of the incidents reported in the information sector involved break-ins through website weaknesses. Miscellaneous errors represented only 1 percent of reports in that industry.

For the government sector, "I think that the raw numbers are actually quite high for things like Web-based attacks and espionage as well," Jacobs said. "But it’s masked because of all of this other data.”

"A lot of that is misdelivery -- which is either attaching the wrong thing to an email or sending the right email to the wrong people," he added. "Or another huge problem is when the mailing machine would get off by one [person] and so it was putting an address on an envelope with somebody else’s personal information inside the envelope."

The percentages in the Verizon study cannot be compared between sectors because they represent the proportion of incidents within each sector.

Based on the raw data, cyberspying in government is comparable to cyberspying in other industries, Jacobs said. "It's just that in other industries we don’t have that mandatory reporting, so we don’t see that level of employee error. We don’t see the misuse," he added. The raw numbers were not disclosed in the study.

More than 50 organizations worldwide contributed to this year's assessment, including law enforcement agencies, government computer security incident response teams, private forensics investigators, security product vendors and public-private information sharing and analysis centers.

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