EDR Modernization: Replacing Legacy AV with Enterprise-Grade Detection
A practical playbook for migrating from legacy antivirus to modern EDR — scoping, vendor evaluation, phased rollout, and the metrics that prove it's working.
Legacy antivirus gives you a false sense of security. Here’s how I approach the migration to real endpoint detection and response.
Assessment First
Before evaluating vendors, audit what you actually have. How many endpoints? What OS mix? What’s the current detection rate? (Hint: if you don’t know your detection rate, that’s your first problem.) Map your compliance requirements — SOC 2, HIPAA, whatever applies — to specific EDR capabilities you’ll need.
Vendor Evaluation Framework
I evaluate EDR platforms on five axes: detection efficacy (do they catch what matters), management overhead (can a small team operate it), integration depth (does it feed into your SIEM/SOAR), platform coverage (macOS + Windows + Linux, not just Windows), and response capabilities (can you isolate/remediate remotely).
Phased Rollout
Never big-bang an EDR migration. Phase 1: deploy in monitor-only mode to a pilot group. This lets you tune detection policies without disrupting work. Phase 2: enable blocking on the pilot group, monitor for false positives for two weeks. Phase 3: expand to 25% of the fleet, then 50%, then full deployment. Each phase gets its own success criteria before advancing.
Proving Value
Track: mean time to detect (MTTD), mean time to respond (MTTR), false positive rate, and coverage percentage. Present these monthly. Security investments that can’t demonstrate measurable improvement are the first to get cut in budget reviews.
Written by Alex Davenport
alexdavenport.dev