Decline In Number Of Critical Vulnerabilities Could Be Deceiving

In 2013, the number of software flaws of critical severity -- as measured by their ranking on the Common Vulnerability Scoring System (CVSS) -- dropped by about 9 percent, according to Hewlett-Packard's 2013 Cyber Risk Report, released on Monday.

Good news for the software industry? Not necessarily, says Jacob West, chief technology officer for HP's enterprise security products group. The company's Zero Day Initiative, which buys vulnerabilities from researchers and then works with vendors to get them fixed, posits that critically rated software flaws are increasingly being sold to penetration testing firms and government agencies -- typically referred to as "gray markets" -- and to criminals on the black market.

"There is an increased value placed on the vulnerabilities that can cause a remote compromise somewhere," West says. "The increased market value is leading more of the total that are discovered to go to gray market or black market destinations than we have seen in the past."

Since 2008, the number of critical vulnerabilities -- typically those with a CVSS of 7.0 and higher -- disclosed each year has fallen. While vulnerability experts are increasingly critical of the CVSS's ability to measure the severity of a vulnerability, the trend appears to indicate that software vendors are succeeding in making exploitable vulnerabilities more difficult to find.

HP sees the trend in a different light, as its own purchases of vulnerabilities has generally fallen. The number of vulnerabilities purchased by its Zero Day Initiative increased in 2013, compared to the prior year, but remains below the purchase levels in 2010 and 2011. West argues that the trend is caused by critical vulnerabilities being sold elsewhere or hoarded by criminal and intelligence organizations.

[Private brokers sell zero-day bugs for anywhere between $40,000 and $160,000 -- and in some cases buyers could end up spending much more for lucrative targets, new analysis says. See Hacking The Zero-Day Vulnerability Market.]

Stefan Frei, research director with NSS Labs, a security information provider, says other players in the market could account for the decrease in both critical vulnerabilities and vulnerabilities sold to white-market bounty programs, such as ZDI. Private vendors, such as Revuln and Exodus Intelligence, are made up of researchers who contributed to HP's Zero Day Initiative and now are competing with the group, he says. In addition, an increasing number of software vendors are offering bounties, including a former notable holdout, Microsoft.

Other private buyers, such as government agencies, are also scooping up exploitable flaws, he says.

"This is stuff that would not pop up otherwise," Frei says. "I would not dare put a number on it, but there is a clear drift" of vulnerabilities to these other markets, he says.

Whether those vulnerabilities are critical or even deserve a critical rating is another point of contention. Only 50 to 60 "truly critical" vulnerabilities are found each year, argues Aaron Portnoy, former manager at HP's ZDI and now vice president of research for Exodus Intelligence. Only software issues that allow reliable remote exploitation should be considered critical, he says.

"I take issue with statements like that [about hundreds of critical flaws], in general," Portnoy says. "The main reason is because the rating system that we use for criticality in our industry is skewed. There really aren't that many vulnerabilities discovered in a year."

Portnoy and other researchers have taken issue with the CVSS as a measure of the severity of vulnerabilities. Last year, researchers criticized the system for its significant shortcomings, finding that the CVSS score for a particular vulnerability did not correlate strongly to whether an exploit was developed for the security issue. Moreover, different companies and vulnerability surveys had widely varying tallies for the number of vulnerabilities reported in any particular year.

HP acknowledged these shortcomings in its report. "While the public repositories provide a glance into the vulnerability landscape, it is limited to reporting those that are publicly disclosed or directly submitted to the organization," the company stated. "This leaves a silo-driven gap for any one organization's ability to speak to the security and vulnerability landscape as a whole."

Anecdotally, researchers are increasingly paid for their vulnerability research, as more bounty programs exist or have been established. Researchers' efforts to get paid for their discoveries and disclosures of significant software vulnerabilities have often fallen flat, but there are now far more opportunities to get some money from vendors, third-party bounty programs, or by selling to the gray market.

Data on the trend, however, is lacking. Gray market sales to governments and penetration testers, for example, appear to be holding steady and will continue to remain a minority of the market, says Adriel Desautels, CEO and manager at Netragard, a security services firm that also brokers vulnerability sales to a variety of undisclosed clients.

"The market goes up and down, and we grow in size, but that growth is not something that we can attribute to an overall market shift," he says.

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