How SSL Intelligence and SSL History Can Supercharge Threat Hunting

SSL certificates are the silent workhorses of the internet. They encrypt data, protect users, and establish trust between websites and visitors. But here's the thing-SSL certificates are also treasure troves of intelligence for cybersecurity professionals. If you can dig into SSL history and use SSL intelligence, you can uncover hidden connections, track down threat actors, and spot vulnerabilities before they're exploited.

Researchers have found that many malware families reuse SSL/TLS certificates, leaving patterns that expose malicious activity. One study identified over 1,700 malware-linked certificates with unique markers. Additionally, 71% of malware uses encryption to hide communications, making SSL intelligence essential for modern threat hunting.

In this article, we will dive into how SSL intelligence, especially historical data, can become critical to your threat-hunting toolkit. Let's begin.

What is SSL intelligence?

SSL intelligence refers to the strategic analysis of SSL/TLS certificates, including their issuers, validity periods, and patterns of reuse across domains and IP addresses. By mapping these connections, security teams can uncover malicious infrastructure, track the movement of adversaries, and even predict potential attack vectors before they materialize.

Why SSL History Matters in Cybersecurity

Every SSL certificate has a story-where it was issued, which domains it's tied to, and even how it's been reused. This kind of data might seem unremarkable at first glance, but it can reveal patterns that are invaluable for tracking down malicious activity.

Take, for example, Hunt.io's recent investigation into the KeyPlug malware. Our cyber threat hunting team uncovered an entire infrastructure of command-and-control (C2) servers by analyzing TLS certificates that were reused across multiple domains. These certificates served as breadcrumbs, leading investigators to GhostWolf-the malicious infrastructure cluster attributed to RedGolf/APT41, a notorious threat actor group. Without access to historical SSL data, these connections might have been invisible.

Or consider the Cyberhaven extension compromise, where attackers used fake SSL certificates to make malicious browser extensions seem legitimate. By examining SSL history, researchers noticed inconsistencies in SSL certificate issuers, with multiple certificates appearing under slightly altered but familiar-sounding names—an often-overlooked tactic in certificate forgery.

By comparing historical SSL data, they connected the dots between seemingly unrelated domains, ultimately exposing a coordinated effort to distribute malicious browser extensions under the guise of legitimate software.

These aren't isolated cases. Time and again, SSL intelligence has proven to be a powerful tool for uncovering and neutralizing threats.

How SSL Intelligence Drives Proactive Threat Hunting

Let's break down some of the ways you can use SSL intelligence to stay ahead of attackers.

1. Uncovering Threat Actor Infrastructure

Threat actors aren't as creative as you might think. They often reuse SSL certificates across different domains to streamline their operations. This is great news for threat hunters because it means patterns can be detected. Analyzing SSL history allows you to map out connections between malicious domains, uncover hidden infrastructure, and identify potential targets before attackers strike.

2. Spotting Rogue Certificates

In supply chain attacks, attackers frequently create rogue certificates to make their operations look legitimate. Monitoring SSL history lets you detect these certificates and understand how they're being used. It's like having a security camera for your digital assets-you can see when something's out of place.

3. Detecting Unauthorized Changes

If an SSL certificate on your domain changes unexpectedly, it's a red flag. Attackers sometimes swap valid certificates with their own to redirect traffic or launch phishing campaigns. By tracking historical SSL data, you can spot these unauthorized changes and act before any damage is done.

Tools for Harnessing SSL Intelligence

Now that we've covered the "why," let's talk about the "how." To effectively use SSL intelligence, you need the right tools. Here are some of the most effective ways to get started:

OpenSSL for Basic Certificate Analysis

OpenSSL is an easy-to-use tool to fetch SSL certificate data. A quick command-line query can give you details about the current certificate, such as its issuer and validity:

openssl s_client -connect example.com:443 -showcerts

This command initiates a connection to example.com on port 443 and retrieves the SSL certificate details. You'll see information like:

• Issuer: Who issued the certificate.

• Validity: The start and expiration dates.

• Subject: The domain(s) covered by the certificate.

However, OpenSSL only shows what's happening right now-it doesn't provide historical SSL data, which is where the real insights often lie.

Online SSL Lookup Services

Web-based tools like SSL Labs make it easy to analyze SSL certificates for small-scale investigations. While these tools are useful for quick checks, they aren't designed for large-scale analysis or tracking SSL history.

Hunt.io's SSL Intelligence

The SSL History tab in Hunt.io's Threat Hunting Platform is great for digging into an attacker's infrastructure. It gives you a clear timeline of SSL/TLS certificates, showing when they were issued, expired, or replaced.

This visibility makes it easier to spot patterns, like certificates being reused across different domains, IPs, or sudden changes that raise red flags. Within the same interface, you can not only view the SSL history but also access the Certificate IPs section to pivot to additional servers using the same certificate over time.

Hunt.io's Certificate IPs feature helps researchers track attacker infrastructure by identifying SSL/TLS certificate reuse across multiple IPs. This visibility can uncover shared infrastructure, detect suspicious hosting providers, and provide leads on potential C2 node activity.

SSL/TLS Certificate Feeds

Hunt.io also offers additional features to gather SSL intelligence, such as monitoring new SSL/TLS certificates or tracking new hostnames found on SSL certificates from our Threat Intelligence Feeds. These features provide more avenues to uncover hidden infrastructure and strengthen threat-hunting efforts.

Advanced SSL Intelligence with HuntSQL™

If you're serious about SSL intelligence, HuntSQL™ is another great source to get SSL intelligence. For instance, it provides both current and historical SSL data. You can query our SQL language to uncover certificate issuers, validity periods, and even patterns of reuse across domains and subdomains.

Here are some query examples:

Search for a Certificate Value

Find all IP and port combinations where a specific certificate value was observed. For example, searching for "AsyncRAT Server" in subject common names reveals all associated hosts and ports.

Query Example:

SELECT ip, port, subject.common_name  

FROM certificates  

WHERE subject.common_name == 'AsyncRAT Server'  

AND timestamp.day gt '2024-01-01'

Output example:

View Certificate History for a Host

Search an IP address to see its certificate activity, including IP, port, subject common names, and timestamps. For example, querying 47.121.120.18 reveals its association with AsyncRAT, showing it first appeared on port 8808 (2024-07-31) before switching to port 7707 (2024-07-30).

Query Example:

SELECT timestamp, ip, port, subject.common_name 

FROM certificates 

WHERE ip == '47.121.120.18' 

AND timestamp.day gt '2024-01-01'

Output example:

This level of detail helps you stay ahead by tracking SSL changes in real-time, spotting suspicious patterns, and connecting the dots between attacker infrastructure-all with just a few queries.

Real Scenarios Where SSL Intelligence Shined

To see SSL intelligence in action, let's explore how it has been used to uncover malicious infrastructure in real-world investigations.

In the DarkPeony investigation, our research team identified recurring patterns in SSL certificates associated with PlugX command and control nodes. By analyzing these certificates, researchers connected seemingly unrelated domains and mapped out the attackers' infrastructure. This kind of intelligence provided clarity on the group's sustained campaigns, allowing teams to track their activity more effectively.

The Earth Baxia case demonstrated another angle of SSL intelligence. Our researchers used SSL certificates and redirects to identify infrastructure linked to PlugX malware. By following these digital breadcrumbs, they uncovered a network of domains and IPs connected to Earth Baxia's operations. This insight was instrumental in revealing the attackers' broader strategy and preventing further compromise.

These investigations also highlight a key takeaway: adversaries are creatures of habit. Even when they change hosting providers or rotate domains, they often reuse SSL certificates across different campaigns. This seemingly small oversight allows threat hunters to establish connections between past and present infrastructure, revealing long-term operational patterns and providing a more complete picture of an attacker’s tactics.

Both cases show how SSL certificate analysis is a powerful tool for uncovering hidden connections and exposing the full scope of an attacker's operations. By leveraging Hunt.io's Threat Hunting Platform, researchers can make these discoveries faster and more accurately.

Why SSL History Should Be Part of Your Strategy

SSL certificates are everywhere. They're used by legitimate businesses, but they're also exploited by attackers. By analyzing both current and historical SSL data, you gain a unique advantage in threat hunting. You can track threat actor infrastructure, detect unauthorized changes, and respond faster to emerging threats.

If you're not already incorporating SSL intelligence into your cybersecurity strategy, now is the time. The insights you'll uncover could be the difference between catching an attack early and dealing with its aftermath.

Put SSL Intelligence to Work for Your Threat Hunting

At Hunt.io, we make SSL intelligence accessible and actionable. Whether you're investigating a specific domain or monitoring a large-scale network, our tools provide the insights you need to stay ahead of the curve.

By leveraging SSL intelligence, you can uncover these hidden networks before they strike. See it in action with Hunt.io-book a free demo today and discover how SSL history can elevate your threat-hunting strategy.