Google Analysis of Zero-Days Exploited in 2019 Finds 'Detection Bias'

Google Project Zero last week released a report on the vulnerabilities exploited in attacks in 2019, and its researchers have drawn some interesting conclusions regarding the detection of zero-days.

Google Project Zero has been tracking vulnerabilities exploited in the wild since 2014 and last year it made available a spreadsheet showing the flaws it has tracked.

The first “Year in Review” report shows that in 2019 there were 20 vulnerabilities that were found to be exploited in the wild, although Project Zero pointed out that these were only the security holes that were detected by the industry, and the actual number of new zero-days exploited last year was likely higher.

The list of vulnerabilities exploited last year includes weaknesses affecting Apple’s iOS, Microsoft’s Windows and Internet Explorer, Google’s Android and Chrome, Mozilla’s Firefox, and Trend Micro’s OfficeScan.

While 11 of the 20 flaws impact Microsoft products — this is five times more compared to Apple and Google products — Project Zero noted that this percentage shows that Microsoft products are a prime target for threat actors, but the number can likely also be attributed to “detection bias.”

“Because Microsoft has been a target before some of the other platforms were even invented, there have been many more years of development into 0-day detection solutions for Microsoft products. Microsoft’s ecosystem also allows for 3rd parties, in addition to Microsoft themself, to deploy detection solutions for 0-days. The more people looking for 0-days using varied detection methodologies suggests more 0-days will be found,” explained Google Project Zero researcher Maddie Stone.

Stone also pointed out that of the 11 zero-days found in Microsoft products, only four were used against Windows 10 users, which could also be an indicator of detection bias.

“Is legacy software really the predominant targets for 0-days in Microsoft Windows, or are we just better at detecting them since this software and these exploit techniques have been around the longest?” the researcher asked.

While there only appear to be a handful of exploited iOS and Android vulnerabilities and no exploited flaws affecting Linux or macOS, this does not necessarily mean these platforms are not targeted. Instead, it shows that the industry should focus more on detecting attacks aimed at these operating systems.

This is also demonstrated by the fact that more than half of the 20 vulnerabilities exploited in 2019 were detected by Clément Lecigne of Google's Threat Analysis Group (7 zero-days) and Kaspersky (4 zero-days).

“If two entities out of the entirety of the global security community are responsible for detecting more than half of the 0-days in a year, that’s a worrying sign for how we’re using our resources,” Stone noted. “The security community has a lot of growth to do in this area to have any confidence that we are detecting the majority of 0-days exploits that are used in the wild.”

The researcher also highlighted that only one of the vulnerabilities exploited last year was discovered internally by the vendor — the same flaw was also independently discovered by an external researcher — which she says is surprising because vendors should be better positioned to detect zero-days.

“This begs the question: are the vendor security teams that have the most access not putting resources towards detecting 0-days, or are they finding them and just not disclosing them when they are found internally?” Stone said. “Either way, this is less than ideal. When you consider the locked down mobile platforms, this is especially worrisome since it’s so difficult for external researchers to get into those platforms and detect exploitation.”

Google Project Zero’s spreadsheet shows that the list for 2020 already includes 11 exploited zero-days, including ones affecting Firefox, Internet Explorer, Chrome, Trend Micro’s OfficeScan, Windows, and Sophos’ XG firewalls.

Related: Google Project Zero Updates Vulnerability Disclosure Policy

Related: Google Researchers Find Multiple Vulnerabilities in Apple's ImageIO Framework

Related: Google Researchers Detail Critical iMessage Vulnerability