SOC 2 and ISO 27001 both expect some form of intrusion detection — a way to notice unauthorized or anomalous activity in your environment. If you're on AWS, the question of whether GuardDuty alone is "enough," or whether you need a separate dedicated IDS product, comes up constantly.
For most companies, GuardDuty alone is sufficient
GuardDuty is a genuine managed threat-detection service — it analyzes CloudTrail, VPC Flow Logs, and DNS logs for known attack patterns, compromised credentials, and anomalous behavior, and it satisfies the "intrusion detection" expectation for the large majority of SOC 2 and ISO 27001 audits for a typical SaaS company. Auditors are generally familiar with it and don't push back on it as insufficient on its own.
What matters more than the specific tool is that you can show:
It's actually enabled across all relevant accounts/regions, not just the ones you happen to look at.
Someone is responsible for reviewing findings — an enabled-but-ignored GuardDuty instance is a weaker control than one with a documented review cadence.
Findings feed into your actual incident response process, not just a dashboard nobody checks.
When a dedicated IDS becomes worth adding
A few situations genuinely call for something beyond GuardDuty:
Host-level visibility. GuardDuty is largely network/API-layer — if a specific customer contract or a stricter framework (e.g. certain PCI DSS scopes) requires host-based intrusion detection (processes, file integrity, syscalls on individual servers), that's a different category of tool GuardDuty doesn't cover.
A specific customer or auditor requirement. Occasionally an enterprise customer's own security questionnaire names a specific tool or capability by name — at that point it's a contractual answer, not a general compliance one.
Non-AWS infrastructure. GuardDuty is AWS-native; if meaningful parts of your stack run elsewhere, you need equivalent coverage there too.
The practical takeaway
Default to enabling GuardDuty account-wide and documenting your review process — that's the right first move and covers most audits outright. Only look at a dedicated IDS product when a specific control, framework scope, or customer requirement calls for something GuardDuty structurally doesn't provide (usually host-level detection), rather than adding a second tool preemptively.