Summary: The National Cyber Security Centre (NCSC) is aware of an ongoing campaign of denial-of-service (DoS) attacks affecting New Zealand entities. The campaign has included the targeting of a number of global entities, predominantly in the financial sector.
The NCSC strongly encourages all organisations in this sector to consider the risk to their organisation of DoS and ensure appropriate mitigations are in place.
The NCSC recommends following the steps provided below, replicated from the Australian Cyber Security Centre. It reflects best practice developed in response to previous denial of service activity.
Preparing for denial-of-service attacks
Before implementing any measures to prepare for denial-of-service attacks, organisations should determine whether a business requirement exists for their online services to withstand denial-of-service attacks, or whether temporary denial of access to online services is acceptable to the organisation.
If organisations wish to increase their ability to withstand denial-of-service attacks, they should, where appropriate and practical, implement the following measures prior to any denial-of-service attacks beginning:
Determine what functionality and quality of service is acceptable to legitimate users of online services, how to maintain such functionality, and what functionality can be lived without during denial-of-service attacks.Discuss with service providers the details of their denial-of-service attack prevention and mitigation strategies. Specifically, the service provider’s:
capacity to withstand denial-of-service attacks
any costs likely to be incurred by customers resulting from denial-of-service attacks
thresholds for notifying customers or turning off their online services during denial-of-service attacks
pre-approved actions that can be undertaken during denial-of-service attacks
denial-of-service attack prevention arrangements with upstream providers (e.g. Tier 2 service providers) to block malicious traffic as far upstream as possible.
Protect organisation domain names by using registrar locking and confirming domain registration details (e.g. contact details) are correct.
Ensure 24×7 contact details are maintained for service providers and that service providers maintain 24×7 contact details for their customers.
Establish additional out-of-band contact details (e.g. mobile phone number and non-organisational email) for service providers to use when normal communication channels fail.
Implement availability monitoring with real-time alerting to detect denial-of-service attacks and measure their impact.
Partition critical online services (e.g. email services) from other online services that are more likely to be targeted (e.g. web hosting services).
Pre-prepare a static version of a website that requires minimal processing and bandwidth in order to facilitate continuity of service when under denial-of-service attacks.
Use cloud-based hosting from a major cloud service provider (preferably from multiple major cloud service providers to obtain redundancy) with high bandwidth and content delivery networks that cache non-dynamic websites.
If using a content delivery network, avoid disclosing the IP address of the web server under the organisation’s control (referred to as the origin web server), and use a firewall to ensure that only the content delivery network can access this web server.
Use a denial-of-service attack mitigation service.
Responding to denial-of-service attacks
Organisations that wish to attempt to withstand denial-of-service attacks, but have not pre- prepared should, where appropriate and practical, implement the following measures, noting that they will be much less effective than had they been able to adequately prepare beforehand:
Discuss with service providers their ability to immediately implement any responsive actions, noting service providers may be unable or unwilling to do so, or may charge additional fees for services not covered in contracts.
Temporarily transfer online services to cloud-based hosting hosted by a major cloud service provider (preferably from multiple major cloud service providers to obtain redundancy) with high bandwidth and content delivery networks that cache non-dynamic websites. If using a content delivery network, avoid disclosing the IP address of the origin web server, and use a firewall to ensure that only the content delivery network can access this web server.
Use a denial-of-service attack mitigation service for the duration of the denial-of-service attacks.
Deliberately disable functionality or remove content from online services that enable the current denial-of-service attack to be effective (e.g. implement a pre-prepared low resource version of the website, remove search functionality, or remove dynamic content or very large files).
Finally, the NCSC recently released a guide to help organisations plan and prepare for cyber security incidents. Download Incident Management: Be Resilient, Be Prepared [PDF, 3.07 MB].