The CISO’s 100-Day Plan — A Roadmap for New Security Leaders By CyberDudeBivash • Date: September 21, 2025 (IST)

TL;DR

First 72 hours: stop the bleeding (privileged MFA, backups/keys, logging, edge devices), establish comms, review open incidents.
Days 1–30 (Stabilize): baselines, crown jewels, identity hygiene, EDR/patch coverage, IR readiness, quick wins.
Days 31–60 (Align): risk register, 12-month roadmap & budget, policy refresh, operating model, vendor rationalization.
Days 61–100 (Execute): tabletop & DR test, OKRs live, talent plan, secure SDLC rollout, board-level narrative and metrics.

The First 72 Hours — “Stop the Bleeding”

Objectives: assure the CEO/Board you have control; reduce catastrophic risk quickly.

Actions (do now)

Privileged access & identity
- Enforce phishing-resistant MFA for all admins; rotate break-glass creds; restrict legacy auth.
- Freeze high-risk changes on SSO/IdP and internet-facing devices.
Backups & crypto
- Verify immutable, offline backups for crown jewels (AD/Entra, critical DBs, core apps).
- Confirm KMS access controls & key rotation; audit last 30 days of key use.
Logging & detection
- Ensure centralized logs for identity, email, endpoints, cloud control planes are flowing to SIEM.
- Turn on high-value detections (new global admin, OAuth app consent, inbox forwarding, web shell indicators).
Perimeter & edge
- Patch/mitigate internet-facing devices (VPN/ADC/WAF); revoke stale sessions; check for webshells.
- Block high-risk file types at email gateway; set DMARC to quarantine if not at reject yet.
IR readiness
- Update call tree, open incident list, and external IR retainer.
- Stand up a single incident channel (e.g., “#security-incidents”) and an exec brief template.

Comms (same day)

5-line note to execs: what’s done, what’s next 7 days, no drama.
Slack/email org-wide: how to report suspicious activity; no-link IT policy for finance/IT comms.

Days 1–30 — Stabilize & Baseline

Goal: know what you’re protecting, who owns it, how it’s exposed, and get the top 10 risks under control.

Discovery & alignment

Stakeholder map: CEO, CIO/CTO, CFO, GC/Privacy, HR, Risk, Internal Audit, BU leads. Bi-weekly 15-minute touchpoints.
Crown jewels: inventory top 10 systems/data sets; record RPO/RTO and business owner.
Asset & identity baseline: % devices with EDR, % users with MFA, # admins by system, external attack surface list.

Quick wins (ship inside 30 days)

Identity hygiene: admin separation, number-matching, conditional access baselines; disable shared admin creds.
Email & web: DMARC→reject, block look-alike domains, URL rewriting/safe browsing, VIP protections (C-suite/AP/HR).
Endpoints: push EDR to ≥ 95% coverage; enable core ASR/ransomware controls.
Vuln mgmt: define SLOs (e.g., 7/30 days for critical/high) and publish the first remediation wave.
IR drills: 60-minute BEC and ransomware tabletop; patch the gaps immediately.
Third parties: create a tiered vendor list; require SSO + logging for Tier-1 SaaS.

Deliverables due by Day 30

Security 1-pager (mission, scope, principles).
Top 10 Risks (heatmap with owners & due dates).
90-day hiring/skills plan and 12-month budget envelope.
Security Service Catalog (what Security provides + SLAs).

Metrics to report (simple)

Admins on phishing-resistant MFA: ≥ 100%
EDR coverage: ≥ 95% endpoints
Mean time to respond (triage): < 30 min
Critical vulns older than SLO: trending down week-over-week

Days 31–60 — Align Strategy, Model, and Money

Goal: convert baselines into a funded, measurable program.

Strategy & governance

Risk register (bow-tie per top risk) with control owners and mitigation plans.
Operating model: define pods (SecOps, IR, IAM, AppSec, CloudSec, GRC, BISO). Publish RACI.
Policies (lightweight): Acceptable Use, Secure Dev, Vulnerability Mgmt, Third-Party Risk, Data Handling, Incident Response.

Roadmap & budget

Draft a 12-month roadmap across 5 tracks: Identity, Endpoint, Cloud, Data, AppSec.
Tie each initiative to risk reduction and business outcomes (uptime, sales velocity, compliance).

Engineering the pipeline

Secure SDLC: threat modeling for Tier-1 apps, SAST/DAST/dep scanning in CI, secrets management, change approvals.
Cloud guardrails: baseline CSPM, IaC validations, break-glass logging, least-priv service principals.

Vendor & cost sanity

Consolidate overlapping tools; prefer platform where 80/20 fit is good.
Turn off shelf-ware; re-allocate to coverage gaps (e.g., EDR/IDP licenses).

Deliverables due by Day 60

Board deck v1 (risk, roadmap, KPI baselines, funding ask).
IR plan with roles, comms tree, evidence handling, and external counsel contact.
Third-party intake workflow (security review + SSO/logging requirements).

Days 61–100 — Execute, Prove, and Communicate

Goal: demonstrate measurable risk reduction and operational discipline.

Controls live

Identity: admin isolation workstations, just-in-time elevation, service principal inventory, OAuth consent governance.
Data: DLP for Tier-1 repos, label/encrypt PII/PHI, egress controls to unknown SaaS.
AppSec: backlog triage, top-10 fix sprint, SBOM capture for critical apps.
Resilience: backup restore test for a crown jewel; publish RTO/RPO results.

Exercises

Full IR exercise (red/blue, injects, exec comms) with lessons learned within 72 h.
BIA drill with top BU to tune recovery priorities.

People & culture

Security champions in each BU; monthly office hours.
Launch micro-trainings: phishing, secrets hygiene, data handling (≤7 minutes each).
Hiring: fill the 2–3 highest-leverage roles (e.g., cloud security engineer, IR lead).

Deliverables due by Day 100

KPI dashboard (below) and Board update v2 with trend lines.
12-month roadmap (final) + quarterly OKRs.
After-action report from exercises and first incidents with closures.

KPIs & Targets (track weekly)

Identity: 100% admins on FIDO2/WebAuthn; stale tokens = 0; OAuth high-priv consents = 0 without review.
Coverage: EDR ≥ 98%; log sources ≥ 95% to SIEM; critical vulns > SLO = 0 on Tier-1.
Detection/Response: MTTD < 30 min; MTTR < 4 h (high-sev); % incidents with full evidence chain ≥ 95%.
Resilience: Successful restore test for ≥ 2 crown jewels per quarter.
Third-party: 100% Tier-1 SaaS behind SSO; 90% with log export enabled.
Culture: security training completion ≥ 95%; # of BU champions onboarded.

Templates

Day-One Email to Staff

Hi all — I’ve joined as CISO. In week one we’re verifying backups, tightening admin access, and improving incident reporting. If you spot anything suspicious, use the “Report Phish” button or email security@. We’ll share simple guidance you can act on right away. Thank you for helping keep customers and colleagues safe. — [Your Name]

Board Slide Outline (10 slides)

Mission & top risks (today)
Recent incidents & lessons
Coverage baselines (identity, EDR, logging)
Quick wins shipped
12-month roadmap (by capability)
Budget & headcount mapped to risk
KPIs (trend lines)
Third-party & compliance posture
Exercises & resilience tests
Decisions needed / asks

Risk Register Columns

Operating Model (example)

SecOps/IR: detection, triage, forensics, purple-team, tabletop.
IAM: identity lifecycle, privileged access, federation, tokens/apps.
AppSec/ProdSec: SDLC, SCA/SAST/DAST, threat modeling, SBOM, bug bounty.
Cloud & Platform Security: guardrails, CSPM, IaC, secrets, workload identity.
Data Security: classification, DLP, encryption, key mgmt.
GRC/Privacy: policies, audits, regs (ISO/SOC2/PCI/HIPAA), risk mgmt.
BISO network: embed champions in BUs; align risk to revenue and operations.

Common Pitfalls (avoid these)

Boiling the ocean; ship visible quick wins first.
UI-only changes with no IaC/CLI trail; create drift and regressions.
Treating security as “IT only”; no business owners for risks.
Tool sprawl; platform mindshare beats niche overlap.
No practice; run tabletops and restore tests or recovery will fail when it matters.

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