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BREACH BRIEF⚪ Informational Advisory

SANS ISC Reports Surge in Calendar-Year Digits Within Passwords, Underscoring Credential Weaknesses

The SANS Internet Storm Center observed a growing use of four‑digit year strings in passwords collected from honeypots, highlighting a predictable pattern that can be exploited in credential‑stuffing attacks. Organizations should reassess password policies and consider stronger authentication controls for third‑party access.

LiveThreat™ Intelligence · 📅 April 09, 2026· 📰 isc.sans.edu
Severity
Informational
AD
Type
Advisory
🎯
Confidence
High
🏢
Affected
4 sector(s)
Actions
3 recommended
📰
Source
isc.sans.edu

SANS ISC Reports Surge in Calendar-Year Digits Within Passwords, Underscoring Credential Weaknesses

What Happened — The SANS Internet Storm Center published a follow‑up analysis showing that attackers continue to observe a high prevalence of numeric year patterns (e.g., “2023”, “1999”) in passwords harvested from honeypots. The study notes a measurable shift toward four‑digit year strings as users comply with frequent‑change policies. Why It Matters for TPRM

  • Predictable year‑based passwords increase the success rate of credential‑stuffing attacks against third‑party vendors.
  • Organizations that enforce regular password rotation without accompanying complexity guidance may inadvertently amplify this risk.

Who Is Affected — All industries that rely on password‑based authentication for SaaS, cloud, and on‑premise services; especially MSPs, IAM providers, and enterprises with legacy password policies.

Recommended Actions

  • Review and tighten vendor password policies: enforce length, mixed‑character sets, and prohibit common year patterns.
  • Deploy password‑less or multi‑factor authentication where feasible.
  • Conduct periodic credential hygiene audits on third‑party access accounts.

Technical Notes — The analysis is based on passive collection from multiple honeypot deployments; no CVEs or direct exploits are cited. The data highlights a behavioral trend rather than a technical vulnerability. Source: SANS ISC Diary – Number Usage in Passwords: Take Two

📰 Original Source
https://isc.sans.edu/diary/rss/32866

This LiveThreat Intelligence Brief is an independent analysis. Read the original reporting at the link above.

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