As reported in the IBM X-Force Threat Intelligence Index 2020, X-Force research teams operate a network of globally distributed spam honeypots, collecting and analyzing billions of unsolicited email items every year. Analysis of data from our spam traps reveals trending tactics that attackers are utilizing in malicious emails, specifically, that threat actors are continuing to target organizations through the exploitation of older Microsoft Word vulnerabilities (CVE-2017-0199 and CVE-2017-11882).
- CVE-2017-0199 was first disclosed and patched in April 2017. It allows an attacker to download and execute a Visual Basic Script containing PowerShell commands after the victim opens a malicious document containing an embedded exploit. Unlike many other Microsoft Word and WordPad exploits, the victim does not need to enable macros or accept any prompts — the document just loads and executes a malicious file of the attacker’s choosing.
- CVE-2017-11882 was first disclosed and patched in November 2017. This vulnerability involves a stack buffer overflow in the Microsoft Equation Editor component of Microsoft Office that allows for remote code execution. Interestingly, the vulnerable component was 17 years old (compiled in 2000) at the time of exploitation and unchanged since its removal in 2018.
These vulnerabilities, which were reported and subsequently issued patches in 2017, are the most frequently used of the top eight vulnerabilities observed in 2019. They were used in nearly 90 percent of malspam messages despite being well-publicized and dated. These findings highlight how delays in patching allow cybercriminals to continue to use old vulnerabilities and still see some success in their attacks.
2 Years and Still Going Strong
In addition to these vulnerabilities’ popularity in malspam, the volume of 2019 network attacks that targeted X-Force-monitored customers while attempting to exploit them was 25 times higher than the combined number of network attacks attempting to exploit similar vulnerabilities that leverage Object Linking and Embedding (OLE).
Our analysts did not observe a commonality regarding the malicious payloads used post-exploitation, which means that using these vulnerabilities is the choice of a wide array of threat actors and not specific to a small number of campaigns or adversarial groups.
Figure 1: Observed usage of top CVEs in 2019 spam emails (Source: IBM X-Force)
Another noteworthy insight from the figure above is that most vulnerabilities commonly used by cybercriminals are older ones. None of the vulnerabilities leveraged in 2019 were disclosed last year and only one was disclosed in 2018. The rest go back as far as 2003, further driving home the point that when it comes to malicious cyber activity, what’s old is new and what’s new is old.
The Allure of Older Vulnerabilities
Why would a wide array of threat actors use the same two old and well-known exploits in so many of their attacks? There are a few possible explanations, but the essence of it is they are cheaper, better documented, battle-tested and more likely to lead to legacy systems that are no longer being patched.
First, the exploits are very convenient for an attacker to use in that they don’t require user interaction. Unlike more recent Word vulnerabilities, which require the attacker to convince the user to enable macros, the exploits for these particular vulnerabilities automatically execute when the document is opened. This can help reduce the chance of arousing user suspicions and, accordingly, increase the rate of success.
Second, since so many different actors use these vulnerabilities, it can complicate attribution, as their widespread usage makes associating them with any particular individual or group difficult.
For example, IBM researchers recently observed threat actors leveraging these CVEs and using a variant of the X-Agent malware, which was historically associated with a threat actor known to IBM as ITG05 (also known as APT28). That threat group has been attributed to Russia’s Main Intelligence Directorate. But while they were being used by highly sophisticated threat actors, these vulnerabilities were also leveraged by low-end spammers dropping commodity malware through massive email campaigns.
The reuse of common exploits is a convenient way to muddy threat actor attribution, especially for groups that wish to remain anonymous in their operations. It can allow threat actors to hide among a large volume of activity, obfuscating their actions.
The third and perhaps most likely reason for the continued use of these vulnerabilities is the simple ease and convenience of generating documents that can exploit them. Because these types of documents are essential to the day-to-day operations of many target organizations, they are often not blocked by enterprise email filters. As a final bonus to threat actors, they are also some of the cheapest exploits cybercriminals can buy.
X-Force’s dark web research of underground forums highlights multiple offerings of free document builders that leverage each of these vulnerabilities. Our team also identified free YouTube videos focused on each vulnerability, illustrating how an attacker can generate a document to exploit these issues.
Figure 2: YouTube videos detailing how to generate documents exploiting CVEs 2017-0199, 2017-11882 (Source: IBM X-Force)
One should keep in mind that successful exploitation of older vulnerabilities is more likely to happen on older, unpatched operating systems (OSs) and legacy systems where OS end-of-life means that no new patches are even available. These kinds of systems are most likely used by organizations that can’t patch due to other issues or priorities. While there are many reasons that can contribute to the decision to defer patching, that decision is never a good one in the long run.
What Can Companies Do With This Sort of Information?
Older vulnerabilities are clearly not going away any time soon, so organizations need to be prepared to defend against their attempted exploitation. IBM X-Force Incident Response and Intelligence Services (IRIS) has the following tips for organizations to better protect themselves:
- Asset management is an ongoing process that should be top of mind for risk management. Part of this process is continually assessing risk to critical systems and considering the consequences of not patching them. Reassess the risks and consider patching and updating operating systems as soon as possible. Reality check: Windows 7’s end-of-life took place on January 14, 2020. Is your organization ready to move to an updated OS?
- On the application level, ensure that patches for productivity suites — especially Microsoft software — are applied as soon as they become available.
- Monitor the organization’s environment for PowerShell callouts that may be attempting to download and execute malicious payloads.
- Continue user education on the risks of opening attachments from unknown sources, as vulnerabilities like these do not require any user interaction beyond opening to cause harm.
- Scope and engage in a vulnerability management program to determine if older vulnerabilities are exposing your environment to exploitation by an attacker.