CyberWire Daily: Research Saturday — “The CVE Countdown Clock”

Date: August 16, 2025
Host: Dave Bittner (N2K Networks)
Guest: Bob Rudis, VP of Data Science at GreyNoise

Overview

This episode centers on emerging research from GreyNoise which explores a fascinating early warning pattern: notable spikes in attacker scanning behavior of enterprise technologies often precede the public release of new significant vulnerabilities (CVEs) by about four to six weeks. Bob Rudis shares the methodology, findings, and implications for defenders, illuminating how organizations can use this “CVE countdown clock” to improve their readiness and response to evolving threats.

Key Discussion Points & Insights

Detecting the Spike-to-CVE Pattern

• Anecdotal to Analytical:

  • Bob Rudis describes how initial "gut feeling" about suspicious upticks in scanning activity led to a formal investigation.
    • “We get this weird spike on some piece of usually enterprise grade edge technology … then, a really interesting or bad or just new set of CVEs that come out like really short period of time later” (00:55, Bob Rudis).

• Data & Methodology:

  • GreyNoise deployed a new sensor architecture (since September last year) to systematically track scanning spikes and correlate them with subsequent CVE disclosures for major technologies.
  • Focused on "enterprise-grade edge technology", filtering out consumer tech like D-Link and Linksys due to their constant background scanning noise.

• Quantified Correlation:

  • Out of ~200 spike events across 6–8 technologies, most led to a related CVE publication within a 4–6 week window.
    • “Between four to six weeks, you’re looking at a new CVE coming out.” (02:58, Bob Rudis)
    • “Across those technologies, there’s at least one to three CVEs that came within that six week time period.” (07:06, Bob Rudis)

Why Do Attackers Scan Before CVEs Go Public?

• Inventory Accumulation & Evasion:
  Attackers probe for old vulnerabilities not necessarily to exploit them, but to stay under defenders’ radar and map which organizations are running specific technologies.

  • “They’re doing this probing against older CVEs because orgs don’t care about the older CVEs … to get under the radar.” (05:18, Bob Rudis)

• Twofold Payoff:

  • If a host is still vulnerable—easy compromise.
  • More often, even if patched, the scan provides up-to-date info for launching targeted attacks when new vulnerabilities drop.

• Who’s Doing It:

  • "A-listers" (nation-state actors) have moved from wide inventory scans to more targeted, infrequent bursts, often leveraging open-source data sets (Shodan, Censys) but resorting to their own scans when freshness is needed.
  • Not a regular heartbeat: “They don’t do the inventory scans with a regularity like they used to do. They do these bursts to try to get under the radar and then, you know, use that data later on.” (16:57, Bob Rudis)

Which Technologies Give Reliable Early Warning Signals? (08:09–09:55)

• High Correlation:
  • Fortinet, Juniper, Palo Alto, SonicWall, Ivanti — “very high signal with this spike to CVE within six weeks.”
  • Cisco — “about 80% correlation.”
• Low/No Correlation:
  • Citrix, Mikrotik, D-Link, Linksys — too much background noise or not enough post-spike CVEs to be actionable.

Defender Takeaways & Recommendations

What Should Defenders Do Upon Spotting a Spike? (17:21–20:53)

• Adaptive Logging:

  • “If you see a spike … that should be a signal that you should flip on maybe some NetFlow logging, flip on like full PCAPs, at least partial … or get full system logging into your expensive Splunk … so that you have that to look for what might be coming.” (17:29, Bob Rudis)
  • The six-week window buys critical time to set up extra monitoring or fast-track patch procedures.

• Resource-Efficient:

  • “It’s a small investment … to potentially save themselves for a really bad attack. … It just seems lately that CVEs come out ... and everyone’s taken by surprise and they just don’t have any time to react. We were hoping with this analysis to give them some tools that they can use to be a bit more prepared.” (20:16, Bob Rudis)

Managing False Positives (21:01–22:29)

• Not Universal:
  • About 20% of spikes did not precede a CVE within six weeks, especially in less-correlated technologies.
  • Emphasized: This is not a magic predictor, but a compelling actionable signal for certain technologies.

Getting Started & Empowering Defenders (22:38–26:58)

• Start Simple:
  • Even small orgs can log hits on older CVEs, analyze for spikes using free tools/SQLite, and regularly check for anomalous upticks.
  • Example: “It literally is that simple: log these events, check it for the spike events and then you do your own comparisons.” (23:09, Bob Rudis)
• Trust Your Instincts:
  • Many defenders have had the “gut call” for years; now there is data to support acting on it.
  • “Everything starts with a gut call … I need to now somehow determine whether my hypothesis is true … urge folks, if you have that gut call, find some way to get someone to give you the time … the resources are pretty much free. And go do that.” (27:10, Bob Rudis).

Notable Quotes & Memorable Moments

• On the pattern’s predictive value:
  • “Between four to six weeks, you’re looking at a new CVE coming out.” (02:58, Bob Rudis)
• On the practical value for defenders:
  • “Any leg up you can get on knowing when you might have to prepare your defenses … is just great, because it’s really expensive to set up extra logging. … We wanted to show some documented evidence, show some correlation.” (02:11, Bob Rudis)
• On listening to intuition:
  • “Everything starts with a gut call … if you have that gut call, find some way to get someone to give you the time … the resources are pretty much free.” (27:10, Bob Rudis)
• Memorable Analogy:
  • “It reminds me of … an old Bob Seger lyric. I saw the lightning and waited on the thunder. You know, the spikes are the lightning and the CVE is the thunder.” (25:06, Interviewer)

Key Timestamps

• 00:55–02:58 — Discovery of the spike–CVE pattern
• 04:34–06:57 — Attacker scanning strategies & rationale
• 08:09–09:55 — Technologies with reliable warning signals
• 12:35–17:20 — Why attacker scanning is visible and how they mask intent
• 17:21–20:53 — Concrete recommendations for defenders
• 21:01–22:29 — Discussion of false positives
• 22:38–26:58 — Steps for defenders to get started; advocating for “gut feeling” analysis
• 25:06 — “Lightning and thunder” analogy

Conclusion

Bob Rudis’s research highlights a valuable, actionable pattern: abnormal scanning spikes on enterprise technology often herald the public disclosure of high-impact vulnerabilities within four to six weeks. By tuning their alerting, logging, and patch operations to these signals—even using basic tools—defenders can get a precious head start, potentially blunting new attack waves.
The episode encourages defenders to trust their instincts and leverage data already available within their own infrastructures, bridging human intuition and empirical validation for better cybersecurity.