[This was originally published on the OSVDB blog.]
Verizon released their yearly Data Breach Investigations Report (DBIR) and it wasn’t too long before I started getting asked about their “Vulnerabilities” section (page 13). After bringing up some highly questionable points about last year’s report regarding vulnerabilities, several people felt that the report did not stand up to scrutiny. With a few questions leveled at me, I was curious if Verizon and partners learned from last year.
This year’s vulnerability data was provided by Kenna Security (formerly Risk I/O), and Verizon “also utilized vulnerability scan data provided by Beyond Trust, Qualys and Tripwire in support of this section.” So the data isn’t from a single vendor, but at least four vendors, giving the impression that the data should be well-rounded, and have less questions than last year.
From the report:
Secondly, attackers automate certain weaponized vulnerabilities and spray and pray them across the internet, sometimes yielding incredible success. The distribution is very similar to last year, with the top 10 vulnerabilities accounting for 85% of successful exploit traffic. While being aware of and fixing these mega-vulns is a solid first step, don’t forget that the other 15% consists of over 900 CVEs, which are also being actively exploited in the wild.
This is not encouraging, as they have 10 vulnerabilities that account for an incredible amount of traffic, and the footnoted list of CVE IDs suggests the same problems as last year. And just like last year, the report does not explain the methodology for detecting the vulnerabilities, does not include details about the generation of the statistics, and provides a loose definition of what “successfully exploited” means. Without more detail it is impossible for others to reproduce their results, and extremely difficult to explain or disclaim them as a third party reading the report. Going to the Kenna Security page about this report doesn’t really yield much clarity, but does highlight another potential flaw in the methodology:
Kenna’s Chief Data Scientist Michael Roytman was the primary author of this year’s “Vulnerabilities” chapter, analyzing a correlated threat data set that spans 200M+ successful exploitations across 500+ common vulnerabilities and exposures from over 20,000 enterprises in more than 150 countries.
It’s subtle, but notice they went through a data set that spans exploitations across “500+ common vulnerabilities and exposures”, also known as CVE. If the data is only looking for CVEs, then there is an incredibly large bias at play from the start, since they are missing at least half of the disclosed vulnerabilities. More importantly, this becomes a game of fractions that the industry is keen to overlook at every opportunity:
- CVE represents approximately half of the disclosed vulnerabilities.
- Vulnerability scanners and IPS/IDS don’t have signatures for all CVE IDs, so they look for some fraction of CVE.
- Detection signatures are often flawed, leading to false positives and false negatives, meaning they are actually detecting a fraction of the CVE IDs they intend to.
Another crucial factor in how this data is generated is in the detection of the exploits. Of the four companies contributing data, one was founded in 2009 (Risk I/O / Kenna) and another in 2006 (Beyond Trust, in the context of this discussion). That leaves Qualys (founded 1999) and Tripwire (founded 1997), who are likely the sources of the signatures that detected the vulnerabilities. For those around in the late 90s, the vulnerability landscape was very different than today, and security products based on signatures back then are in some ways considered rudimentary compared to today. Over time, most security products do not revisit older signatures to improve them unless they have to, often due to customer demand. Newly formed companies basically never go back and write signatures for vulnerabilities from 1999. So it stands to reason that the detection of these issues are based on Qualys and/or Tripwire’s detection capabilities, and the signatures detecting these vulnerabilities are likely outdated and not as well-constructed as compared to their more recent signatures.
That leads us to ask, how many vulnerabilities are these companies really looking for? Where did the detection signatures originate and how accurate are they? While the DBIR does disclaim that the data used is a sample, they also admit “bias undoubtedly exists”. However, they don’t warn the reader of these extremely limiting caveats that put the entire data set into a perspective clearly showing strong bias. This, combined with the lack of detailed methodology for how these vulnerabilities are detected and correlated to measure ‘success’, ultimately means this data has little value other than for inclusion in pedestrian reports on vulnerabilities.
With that in mind, I can only go by what information is available. We’ll start with the concise list of the top 10 CVE IDs these four vulnerability intelligence providers say are being exploited the most, and Verizon labels as “successfully exploited”:
- 2015-03-05 – CVE-2015-1637 – Microsoft Windows Secure Channel (Schannel) RSA Temporary Key Handling EXPORT_RSA Ciphers Downgrade MitM (FREAK)
- 2015-01-06 – CVE-2015-0204 – OpenSSL RSA Temporary Key Handling EXPORT_RSA Ciphers Downgrade MitM (FREAK)
- 2012-02-25 – CVE-2012-1054 – Puppet k5login File Symlink File Overwrite Local Privilege Escalation
- 2011-07-19 – CVE-2011-0877 – Oracle Enterprise Manager Grid Control Instance Management Unspecified Remote Issue (2011-0877)
- 2004-02-10 – CVE-2003-0818 – Microsoft Windows ASN.1 Library (MSASN1.DLL) BER Encoding Handling Remote Integer Overflows
- 2002-01-15 – CVE-2002-0126 – BlackMoon FTP Server Multiple Command Remote Overflow
- 2001-12-26 – CVE-2002-0953 – PHPAddress globals.php LangCookie Parameter Remote File Inclusion
- 2001-12-20 – CVE-2001-0876 – Microsoft Windows Universal Plug and Play NOTIFY Directive URL Handling Remote Overflow
- 2001-04-13 – CVE-2001-0680 – QVT/Net / Term FTP Server LIST Command Traversal Remote File Access
- 1999-11-22 – CVE-1999-1058 – Vermillion FTPD Long CWD Command Handling Remote Overflow DoS
This list should raise serious red flags for anyone passingly familiar with vulnerabilities. Not only do we have very odd ‘top 10’ lists from last year and this year, but there is little overlap between them. How does 2015 show a top 10 list exploiting eight vulnerabilities with CVE identifiers between 1999 and 2002, meaning they had been exploited so much as many as thirteen years later, only to see them all drop off the list this year, to be replaced by new 15+ year old vulnerabilities? In addition to this oddity, there are more considerations leading to my top 10 list of questions about their list:
- How does a local vulnerability based on a symlink overwrite flaw (CVE-2012-1054) make it into a top 10 list of “85% of successful exploit traffic“?
- How does a local vulnerability in Puppet rank #3 on this list, given the install base of Puppet as compared to Adobe or Java?
- If they are detecting exploits on the wire, shouldn’t we see Java, Adobe Reader, and Adobe Flash somewhere on the list? The “Slow and steady—but how slow?” section even talks about time-to-exploit for Adobe.
- Why doesn’t this list remotely match US-CERT’s “Top 30 Targeted High Risk Vulnerabilities” that includes vulnerabilities back to 2006, but not a single one listed above?
- How does a vulnerability that by all accounts is so vague, that it has to be distinguished by the vendor issued CVE ID (CVE-2011-0877), have a signature and get exploited so much?
- How does a vulnerability in Oracle Enterprise Manager Grid Control show up as #4, when no Oracle Database vulnerabilities appear?
- How do you distinguish an FTP LIST command exploit from one vendor to another? (e.g. CVE-2005-2726, CVE-2002-0558, CVE-2001-0933, CVE-2001-0680) According to the one-liner methodology, this is done via pairing SIEM data, suggesting that BlackMoon and Vermillion are that popular today.
- Yet, how does a remote DoS in an Windows-based FTP program that doesn’t appear to have been distributed for a decade make it on this list? Are people really conducting targeted DoS attacks against this software?
- Is BlackMoon FTP Server really that prevalent to be exploited so often?
- Or is there a problem in generating this data, which would be more easily attributed to loose signatures detecting FTP attacks regardless of vendor?
Figure 12 in the report, which is described as “Count of CVEs exploited in 2015 by CVE publication date” is a curious thing to include, as the CVE publication date is very distinct from the vulnerability disclosure date. While a large percentage of CVE publication dates are within seven days of disclosure, many are not (e.g. CVE-2015-8852 disclosed 2015-03-23 and CVE publication on 2016-04-26). Enough to make this chart questionable as far as the insight it provides. Taking the data as presented, are they really saying that only ~ 73 vulnerabilities with a 2015 ID were successfully exploited in 2015 across “millions of successful real-world exploitations“? Given that 40 vulnerabilities were discovered in the wild, 33 of which have 2015 CVE IDs, that means that only ~40 other 2015 vulnerabilities were successfully exploited? If that is the takeaway, how is the security industry unable to stop the increasing wave of data breaches, the same kinds that led to this report? Something doesn’t add up here.
While people are cheering about the DBIR disclaiming there is sample bias (and not really enumerating it), they ignore the measurement bias, don’t speak to publication bias, don’t explain the attrition bias between 2015 and 2016, or potential chaining bias. As usual, the media is happy to glom onto such reports without asking any of these questions or providing critical analysis. As an industry, we need to keep challenging metrics and statistics to ensure they are not only accurate, but provide meaning that benefits us.
4/28/2016 – According to Gabe (@gdbassett), the list of CVEs in the DBIR is incorrect. He posted a new list of CVEs (mostly the same) via Twitter in a reply to Andreas Lindh who was surprised at the top ten list of vulnerabilities as well. Gabe also confirmed that afterwards they “compared the figure CVEs (listed above) against the raw data. After removing non-confirmed breaches, they match.” He went on to link to another source showing “data” about one of the CVEs, that really doesn’t mean anything without more context. Meanwhile, Michael Roytman, who did the vulnerability section of the report confirmed that he/Kenna would be responding to this blog with one of their own.
I hate to harp on simple transposition style mistakes in a report, but given the severity behind using numeric identifiers for vulnerabilities, it seems like that should have been double and triple-checked. Even then, I don’t understand how someone familiar with vulnerabilities could see either list and not ask many of the same questions I did, or provide more information in the report to back the claims. That said, let’s look at Gabe’s new list of CVEs. Bold and links are used to highlight the new ones:
- 2015-03-05 – 2015-1637 – Microsoft Windows Secure Channel (Schannel) RSA Temporary Key Handling EXPORT_RSA Ciphers Downgrade MitM (FREAK)
- 2015-01-06 – 2015-0204 – OpenSSL RSA Temporary Key Handling EXPORT_RSA Ciphers Downgrade MitM (FREAK)
- 2004-02-10 – 2003-0818 – Microsoft Windows ASN.1 Library (MSASN1.DLL) BER Encoding Handling Remote Integer Overflows
- 2002-07-22 – 2002-1054 – Pablo FTP Server LIST Command Arbitrary Directory Listing Remote Information Disclosure
- 2002-01-15 – 2002-0126 – BlackMoon FTP Server Multiple Command Remote Overflow
- 2001-12-26 – 2002-0953 – PHPAddress globals.php LangCookie Parameter Remote File Inclusion
- 2001-12-20 – 2001-0877 – Microsoft Windows Universal Plug and Play NOTIFY Request Remote DoS
- 2001-12-20 – 2001-0876 – Microsoft Windows Universal Plug and Play NOTIFY Directive URL Handling Remote Overflow
- 2001-04-13 – 2001-0680 – QVT/Net / Term FTP Server LIST Command Traversal Remote File Access
- 1999-11-22 – 1999-1058 – Vermillion FTPD Long CWD Command Handling Remote Overflow DoS
The list gained another FTP server issue that doesn’t necessarily lead to privileges, and another remote denial of service attack, while losing the Puppet symlink (CVE-2012-1054) and the vague Oracle Enterprise Manager issue (CVE-2011-0877). All said and done, the list is just as confusing as before, perhaps more so. That gives us four FTP vulnerabilities, only one of which leads to remote code execution, and two denial of service attacks, that gain no real privileges for an attacker. As Andreas Lindh points out, that I failed to highlight, having a man-in-the-middle vulnerability occupy two spots on this list is also baffling in the context of the volume of attacks stated. Also note that with the addition of CVE-2002-1054 (Pablo FTP), there are now two vulnerabilities that appear on the DBIR 2015 and DBIR 2016 top ten CVE list.
Hopefully the forthcoming blog from Michael Roytman will shed some light on these issues.