How do you stop a Zero-days

How do you stop a zero-day?

That’s a loaded question. If you’re expecting a simple sales answer, you’re asking the wrong question. (You will however get vendors going straight into Unsupervised Learning, Machine Learning and UEBA to detect anomalies, but thats a conversation on AI ) Also, the question should be phrased, How do you mitigate Zero-Day threats?

Grasshopper, continue reading to learn some wisdom, I provide 20 years of my knowlege for free.

The real question is: are you aware of any exploits that haven’t yet been classified as zero-days? Do you think your systems are vulnerable to attacks from unknown or known zero-days? These threats exist right now, we’ve seen them many times before.

Humans have a psychological safety mechanism called normalcy bias, it helps us avoid constant fear. But it also makes people forget past crises and assume they won’t happen again. The same mindset applies to zero-days. So if you ask me how to stop one, I’ll ask you instead: how many known zero-days have you assessed that could affect your systems? And what type of zero day / initial access vectors are you most concerned about?

Let me ask you: have you conducted a threat modeling exercise against your systems to determine if you could be affected by the last few zero-days or their variations?

  1. MOVEit Transfer vulnerability (CVE‑2023‑34362) exploited by the Cl0p ransomware group. Attackers used a previously unknown SQL‑injection zero‑day to install a web shell (LEMURLOOT) and exfiltrate large volumes of data from thousands of internet‑facing servers. akamai.com+3CISA+3Wikipedia+3
  2. Microsoft SharePoint Server zero‑day (variant of CVE‑2025‑49706) exploited in July 2025. Attackers used the flaw to gain access to on‑premises SharePoint servers in government, education, energy and telecom sectors; stole credentials and exfiltrated data. The Washington Post+1

I’ve been collecting actual Zero-Days exploit video and here are a few for your viewing please, You can ask me the question again after you research all of this content and lets have a intelligent conversation, and lets both have a serious conversation as we all need to step up in this cyber industry.

MAIL MARSHAL DEMO

Allot of customers ask; “Can you detect Zero-days”, most Cyber vendors, will give you a marketing answer, and really, that is a simple question to a exhaustive topic. But, the reality is, that detecting zero-days is near impossible. However, this video is the first, I’ve seen that get close to detecting zero-days. Using a very funky tool to detect a BROP attack, or any other kind of buffer-overflow attack. ZeroDetect – https://github.com/polyverse/zerotect

Below: a compact table mapping MITRE ATT&CK initial-access techniques to real historical zero-day CVEs or incidents. Each row shows the technique, the specific zero-day (CVE or incident), a one-line description, and a source.

MITRE Initial Access (technique)Zero-day / Incident (reference)One-line description
Phishing (spearphishing attachment / link)CVE-2017-0199. Microsoft Word RTF remote code execution. NVDMalicious Word/RTF sent by email executed embedded code when opened.
Drive-by compromise (malicious web content)CVE-2014-1776. Internet Explorer use-after-free zero-day. NVD+1Visiting a compromised site triggered remote code execution in IE.
Exploit public-facing applicationCVE-2021-26855 (ProxyLogon). Microsoft Exchange SSRF/RCE exploited in 2021. NVDInternet-facing Exchange servers were remotely exploited without auth.
External remote services (VPN/RDP)CVE-2019-11510. Pulse Secure VPN arbitrary file read exploited in the wild. CISAAttackers used the VPN flaw to access credentials and internal resources.
Supply-chain / Software updateSUNBURST / SolarWinds supply-chain backdoor (2020). Rapid7+1Malicious Orion update delivered a backdoor to thousands of orgs.
Trusted relationship / third-partyCVE-2018-8174 (“Double Kill”) VBScript zero-day used in targeted lures. 360 Total Security Blog+1Malicious documents or sites used VBScript engine bug to run code.
Valid accounts (credential theft / bypass)ProxyLogon / Exchange chain and associated token/credential theft in 2021 incidents. NVDAfter initial exploit actors harvested credentials/tokens to persist.
Removable media (autorun / file parsing)CVE-2010-2568. Windows Shell LNK shortcut parsing exploited by Stuxnet. Microsoft Learn+1Inserting USB with crafted LNK triggered code execution without user opening.
Document-renderer zero-day (office/viewer)CVE-2021-40444. MSHTML/Office RCE delivered via crafted Office docs. Microsoft+1Malicious Office documents exploited MSHTML rendering to run code.

Zero-day attacks exploit unknown vulnerabilities before vendors release patches. Because they’re undiscovered, prevention is impossible, but mitigation is achievable through layered defense and proactive monitoring.

1. Detect Behavior, Not Signatures
Use EDR or XDR to identify anomalies such as abnormal process creation, privilege escalation, or memory injection.

2. Minimize Attack Surface
Disable unnecessary services, ports, and software to reduce potential exploit points.

3. Isolate Risky Applications
Contain browsers, email clients, and document viewers inside sandboxes or virtual environments.

4. Enable Exploit Mitigation Controls
Use OS-level protections like ASLR, DEP, SELinux, and Control Flow Guard to break exploit chains even without patches.

5. Practice Threat Hunting
Regularly analyze telemetry and logs to find patterns suggesting exploitation of unknown flaws.

6. Adopt Zero Trust Principles
Assume breach, verify every access attempt, and enforce least privilege at all times.

Zero-days can’t be eliminated, but disciplined detection, segmentation, and resilience make them manageable.

Step-by-Step Process to Stop (Mitigate) Zero-Days

  1. Patch management: Keep OS, applications, and firmware updated.
  2. Endpoint protection: Use reputable EDR/XDR with behavioral detection and rollback.
  3. IPS/IDS
  4. Application control: Whitelist trusted binaries; block unsigned macros and scripts.
  5. Least privilege: Remove admin rights for daily users; enforce MFA.
  6. Backup strategy: Maintain offline, immutable backups; test restoration regularly.
  7. Network segmentation: Limit lateral movement via VLANs, firewalls, and zero trust policies.
  8. Email filtering: Block phishing, attachments, and URLs with sandboxing.
  9. Threat intelligence: Monitor IOCs and TTPs; use automated blocking.
  10. Incident response plan/DFIR RETAINER: Predefine containment, eradication, and recovery steps.
  11. User training: Teach recognition of phishing and malicious links.
  12. For enterprises: integrate EDR + SIEM + SOAR to automate ransomware detection and response.

Reference