Hardening Remote Desktop Protocol Against Brute Force Intrusions
Remote Desktop Protocol sits at the heart of countless Australian workplaces, letting staff reach servers, point-of-sale systems, and engineering rigs from a home desk in Cottesloe or a branch in Tamworth. The protocol is convenient, but its exposure to the public internet has made it a perennial favourite for password-spray and credential-stuffing campaigns.
The Australian Cyber Security Centre has repeatedly warned that adversaries scan Australian IP ranges for open port 3389, often within minutes of a new host coming online. Following the Essential Eight maturity model is no longer optional for organisations subject to the Security of Critical Infrastructure (SOCI) Act or agencies aligning with the Information Security Registered Assessors Program (IRAP).
Infoziant Security works with enterprises, government bodies, financial institutions, and healthcare providers across the country to lock down remote access before attackers get a foothold. The playbook below distils what those engagements typically surface, from basic configuration hygiene to round-the-clock detection.
Why RDP Remains a Prime Target
RDP was never designed with hostile internet exposure in mind. Microsoft has shipped Network Level Authentication since Vista, yet many Australian small businesses still rely on default settings inherited from a rushed pandemic migration.
Threat actors know that one compromised administrator account can unlock Active Directory, finance systems, and patient records within the My Health Records ecosystem. Modern brute force tools distribute attempts across thousands of IP addresses to slip past crude threshold defences.
The ACSC's annual cyber threat report consistently lists unauthorised access among the top incident categories reported under the Notifiable Data Breaches scheme. A successful intrusion in a Brisbane logistics firm brings downtime plus mandatory reporting to the Office of the Australian Information Commissioner.
Lock Down Account Access and Authentication
The cheapest win is enforcing account lockout policies. Configuring a 10-minute lockout after five incorrect guesses forces attackers to slow their attempts or rotate IPs, raising their cost of doing business.
Password hygiene matters as much as policy. Replace default administrator names with unique service accounts, and apply the passphrases favoured by the ASD's cyber.gov.au guidance: four or five unrelated words that resist dictionary attacks without being impossible for staff in a busy Sydney CBD call centre to recall.
Wherever possible, integrate RDP sign-in with a directory service that supports conditional access, mirroring the controls already protecting Microsoft 365 tenants used by most Australian government departments and ASX-listed firms.
Hide RDP from the Public Internet
Putting RDP directly on a public IP is the single riskiest configuration a business can run. Scanning services like Shodan still reveal thousands of Australian endpoints listening on port 3389, from retail outlets in Hobart to consultancies in Adelaide.
Place RDP behind a virtual private network, ideally with certificate pinning on managed devices. The Australian Prudential Regulation Authority's CPS 234 standard implicitly expects this segmentation for any entity it oversees, and the same logic protects a tradie running a single Windows server from a shed in the Yarra Valley.
If a VPN is genuinely out of reach, change the listening port, restrict source IPs with allow lists, and front the service with a hardened bastion host. None of these are substitutes for a VPN, but together they meaningfully shrink the attack window.
Require Multi-Factor Authentication for Every Session
A username and password, even rotated weekly, can be phished or sprayed. Multi-factor authentication raises the bar so high that brute force becomes economically irrational for the attacker.
Tools such as Microsoft Authenticator, FIDO2 hardware tokens, or smart cards from Australian defence suppliers can be bolted onto RDP via Remote Desktop Gateway or third-party wrappers. For entities operating under the Protective Security Policy Framework, this is effectively non-negotiable.
Phishing-resistant factors beat push notifications every time. Where regulators such as AUSTRAC are watching financial transactions, an MFA compromise is treated as a control failure rather than an isolated user mistake.
Patch, Configure, and Harden the Host
Brute force is rarely the last step in an intrusion. Once attackers are logged in, they look for unpatched vulnerabilities, disabled Defender features, and stored credentials in memory.
Apply Microsoft's monthly cumulative updates without delay, and review Group Policy against the ASD's hardening guide. Disable deprecated ciphers, restrict NLA to supported authentication modes, and enable Restricted Admin mode where appropriate.
Disable clipboard redirection, drive redirection, and Plug and Play device redirection on sensitive hosts handling payment data or clinical records. These features were designed for convenience, not for environments where a single compromised account could expose patient identifiers protected by the Privacy Act 1988.
Monitor, Detect, and Respond Around the Clock
Even well-hardened RDP will eventually face a determined attempt, and that is where visibility becomes the decisive control. Forward Windows event logs 4625, 4624, and 4778 into a SIEM and write correlation rules that flag impossible travel, logon bursts, and off-hours activity.
Infoziant Security's managed detection service watches these events for Australian customers around the clock, blending local ACSC threat intelligence with global feeds. When a brute force pattern emerges, automated playbooks can disable the account and notify the in-house IT lead within minutes.
Finally, rehearse the response. A quarterly tabletop exercise involving the helpdesk, the security team, and the legal contact responsible for OAIC notifications will shorten the gap between detection and the statutory 72-hour breach assessment window.
Practical Recommendations for a Tighter RDP Posture
- Restrict RDP to the internal network or behind a VPN
- Enforce account lockout after five failed attempts
- Require phishing-resistant multi-factor authentication
- Apply monthly cumulative updates and review hardening baselines
- Forward authentication logs to a SIEM with tuned correlation alerts
- Disable clipboard and printer redirection on production hosts
- Conduct quarterly tabletop exercises covering RDP compromise scenarios
Reach out to Infoziant Security for a free VAPT report and a trial-based engagement that maps directly onto Essential Eight maturity targets and SOCI Act obligations. The first session outlines concrete findings, a prioritised remediation roadmap, and a quote that scales with the size of your Australian operation. Locking down remote access is one of the highest-return investments a security budget can make this financial year.
