Ensure High Availability for Online Services
Online services should switch easily between zones to maintain availability.
Plain language
This control ensures that your online business services stay available no matter what. If a problem happens in one area, the service can automatically switch to another area to keep running. This matters because if your online service goes down, you could lose customers, income, and trust.
Framework
ASD Information Security Manual (ISM)
Control effect
Preventative
Classifications
NC, OS, P, S, TS
ISM last updated
Nov 2021
Control Stack last updated
19 Mar 2026
E8 maturity levels
N/A
Guideline
Guidelines for networkingOfficial control statement
Where a high availability requirement exists for online services, the services are architected to automatically transition between availability zones.
Why it matters
Without multi-zone automatic failover, a single availability zone outage can take the service offline, disrupting operations and potentially causing financial loss and reputational damage.
Operational notes
Regularly test automatic multi-zone failover to verify the service transitions between availability zones during a zone outage; record results and tune health checks, routing and deployment settings.
Implementation tips
- System owners should work with IT personnel to determine the availability zones for the online services. They can collaborate to understand which locations or cloud providers their services run from. This can be done with a map or list showing how services are set up to switch between zones.
- IT teams should configure online services to automatically detect failures and switch to a backup zone. They can do this by setting up software rules that monitor the server health and switch servers if a problem is found. This typically involves using cloud provider tools for automatic failover settings.
- Managers responsible for business operations should ensure there's a service impact analysis plan. This involves documenting what happens if your service goes offline and prioritising which services need high availability. They can gather key staff members for a planning session to develop this document.
- Procurement teams must confirm that service agreements with cloud providers include high availability options. Checking contract terms for dynamics like uptime guarantees and regional flexibility is essential. They can consult legal resources to ensure these terms are clear and enforceable.
- IT leaders should organise regular testing of the failover mechanisms. This could involve scheduled drills where the system is deliberately taken offline to observe if it correctly switches to a backup zone. These tests should be logged and reviewed to find any issues and ensure everything works as intended.
Audit / evidence tips
-
Askthe failover configuration documentation: Request written records or diagrams showing how services are set to automatically change zones
Goodwill have dated documents showing specific instructions and responsible parties for each step
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Aska copy of the contract with cloud providers: Request agreements that cover high availability and failover capabilities
Goodcontract will clearly specify terms like '99.9% uptime' and procedures for when systems fail
-
Askthe business impact analysis document: Request a document that sets out which services require high availability and potential impacts of downtime
-
Aska schedule of service checks and updates: Request evidence of regular reviews and updates to the system's resilience setup
Goodschedule will clearly document regular checks, responsible individuals, and any updates following checks
Cross-framework mappings
How ISM-1580 relates to controls across ISO/IEC 27001, Essential Eight, and ASD ISM.
ISO 27001
| Control | Notes | Details |
|---|---|---|
| layers Partially meets (1) expand_less | ||
| Annex A 5.30 | ISM-1580 requires that where high availability is needed for online services, those services are architected to automatically transition ... | |
| sync_alt Partially overlaps (1) expand_less | ||
| Annex A 7.11 | ISM-1580 requires online services with high availability needs to automatically transition between availability zones to maintain service... | |
These mappings show relationships between controls across frameworks. They do not imply full equivalence or certification.