This guidance is based on the Australian Government best practice guide to mitigating cyber security incidents, performing vulnerability assessments and penetration testing Commonwealth organisations.
Prior to implementing any of the mitigation strategies, organisations need to identify their assets and perform a risk assessment to identify the level of protection required from various cyber threats. Furthermore, organisations require motivation to improve their cyber security posture, supportive executives, access to skilled cyber security professionals and adequate financial resources. Motivators can include a significant cyber security incident, a penetration test, mandatory data breach reporting, mandatory compliance, and evidence of a lower cyber security posture or higher threat exposure than previously realised.
Strategies to mitigate cyber security incidents
| Relative Security Effectiveness Rating | Mitigation Strategy | Potential User Resistance |
Upfront Cost (staff, software and hardware) |
Ongoing Maintenance Cost |
| Mitigation Strategies to Prevent Malware Delivery and Execution: | ||||
| Essential | Application control to prevent execution of unapproved/malicious programs including .exe, DLL, scripts (e.g. Windows Script Host, PowerShell and HTA) and installers. | Medium | High | Medium |
| Essential | Patch applications (e.g. Flash, web browsers, Microsoft Office, Java and PDF viewers). Patch/mitigate computers with ‘extreme risk’ security vulnerabilities within 48 hours. Use the latest version of applications. | Low | High | High |
| Essential | Configure Microsoft Office macro settings to block macros from the internet, and only allow vetted macros either in ‘trusted locations’ with limited write access or digitally signed with a trusted certificate. | Medium | Medium | Medium |
| Essential | User application hardening. Configure web browsers to block Flash (ideally uninstall it), ads and Java on the internet. Disable unneeded features in Microsoft Office (e.g. OLE), web browsers and PDF viewers. | Medium | Medium | Medium |
| Excellent | Automated dynamic analysis of email and web content run in a sandbox, blocked if suspicious behaviour is identified (e.g. network traffic, new or modified files, or other system configuration changes). | Low | High | Medium |
| Excellent | Email content filtering. Allow only approved attachment types (including in archives and nested archives). Analyse/sanitise hyperlinks, PDF and Microsoft Office attachments. Quarantine Microsoft Office macros. | Medium | Medium | Medium |
| Excellent | Web content filtering. Allow only approved types of web content and websites with good reputation ratings. Block access to malicious domains and IP addresses, ads, anonymity networks and free domains. | Medium | Medium | Medium |
| Excellent | Deny corporate computers direct internet connectivity. Use a gateway firewall to require use of a split DNS server, an email server and an authenticated web proxy server for outbound web connections. | Medium | Medium | Low |
| Excellent | Operating system generic exploit mitigation e.g. Data Execution Prevention (DEP), Address Space Layout Randomisation (ASLR) and Enhanced Mitigation Experience Toolkit (EMET). | Low | Low | Low |
| Very Good | Server application hardening especially internet-accessible web applications (sanitise input and use TLS not SSL) and databases, as well as applications that access important (sensitive/high-availability) data. | Low | Medium | Medium |
| Very Good | Operating system hardening (including for network devices) based on a Standard Operating Environment, disabling unneeded functionality (e.g. RDP, AutoRun, LanMan, SMB/NetBIOS, LLMNR and WPAD). | Medium | Medium | Low |
| Very Good | Antivirus software using heuristics and reputation ratings to check a file’s prevalence and digital signature prior to execution. Use antivirus software from different vendors for gateways versus computers. | Low | Low | Low |
| Very Good | Control removable storage media and connected devices. Block unapproved CD/DVD/USB storage media. Block connectivity with unapproved smartphones, tablets and Bluetooth/Wi-Fi/3G/4G/5G devices. | High | High | Medium |
| Very Good | Block spoofed emails. Use Sender Policy Framework (SPF) or Sender ID to check incoming emails. Use ‘hard fail’ SPF TXT and DMARC DNS records to mitigate emails that spoof the organisation’s domain. | Low | Low | Low |
| Good | User education. Avoid phishing emails (e.g. with links to login to fake websites), weak passphrases, passphrase reuse, as well as unapproved: removable storage media, connected devices and cloud services. | Medium | High | Medium |
| Limited | Antivirus software with up-to-date signatures to identify malware, from a vendor that rapidly adds signatures for new malware. Use antivirus software from different vendors for gateways versus computers. | Low | Low | Low |
| Limited | TLS encryption between email servers to help prevent legitimate emails being intercepted and subsequently leveraged for social engineering. Perform content scanning after email traffic is decrypted. | Low | Low | Low |
| Mitigation Strategies to Limit the Extent of Cyber Security Incidents: | ||||
| Essential | Restrict administrative privileges to operating systems and applications based on user duties. Regularly revalidate the need for privileges. Don’t use privileged accounts for reading email and web browsing. | Medium | High | Medium |
| Essential | Patch operating systems. Patch/mitigate computers (including network devices) with ‘extreme risk’ security vulnerabilities within 48 hours. Use the latest operating system version. Don’t use unsupported versions. | Low | Medium | Medium |
| Essential | Multi-factor authentication including for VPNs, RDP, SSH and other remote access, and for all users when they perform a privileged action or access an important (sensitive/high-availability) data repository. | Medium | High | Medium |
| Excellent | Disable local administrator accounts or assign passphrases that are random and unique for each computer’s local administrator account to prevent propagation using shared local administrator credentials. | Low | Medium | Low |
| Excellent | Network segmentation. Deny traffic between computers unless required. Constrain devices with low assurance (e.g. BYOD and IoT). Restrict access to network drives and data repositories based on user duties. | Low | High | Medium |
| Excellent | Protect authentication credentials. Remove CPassword values (MS14-025). Configure WDigest (KB2871997). Use Credential Guard. Change default passphrases. Require long complex passphrases. | Medium | Medium | Low |
| Very Good | Non-persistent virtualised sandboxed environment, denying access to important (sensitive/high-availability) data, for risky activities (e.g. web browsing, and viewing untrusted Microsoft Office and PDF files). | Medium | Medium | Medium |
| Very Good | Software-based application firewall, blocking incoming network traffic that is malicious/unauthorised, and denying network traffic by default (e.g. unneeded/unauthorised RDP and SMB/NetBIOS traffic). | Low | Medium | Medium |
| Very Good | Software-based application firewall, blocking outgoing network traffic that is not generated by approved/trusted programs, and denying network traffic by default. | Medium | Medium | Medium |
| Very Good | Outbound web and email data loss prevention. Block unapproved cloud computing services. Log recipient, size and frequency of outbound emails. Block and log emails with sensitive words or data patterns. | Medium | Medium | Medium |
| Mitigation Strategies to Detect Cyber Security Incidents and Respond: | ||||
| Excellent | Continuous incident detection and response with automated immediate analysis of centralised time-synchronised logs of allowed and denied computer events, authentication, file access and network activity. | Low | Very High | Very High |
| Very Good | Host-based intrusion detection/prevention system to identify anomalous behaviour during program execution (e.g. process injection, keystroke logging, driver loading and persistence). | Low | Medium | Medium |
| Very Good | Endpoint detection and response software on all computers to centrally log system behaviour and facilitate incident response. Microsoft’s free SysMon tool is an entry level option. | Low | Medium | Medium |
| Very Good | Hunt to discover incidents based on knowledge of adversary tradecraft. Leverage threat intelligence consisting of analysed threat data with context enabling mitigating action, not just indicators of compromise. | Low | Very High | Very High |
| Limited | Network-based intrusion detection/prevention system using signatures and heuristics to identify anomalous traffic both internally and crossing network perimeter boundaries. | Low | High | Medium |
| Limited | Capture network traffic to and from corporate computers storing important data or considered as critical assets, and network traffic traversing the network perimeter, to perform incident detection and analysis. | Low | High | Medium |
| Mitigation Strategies to Recover Data and System Availability: | ||||
| Essential | Daily backups of important new/changed data, software and configuration settings, stored disconnected, retained for at least three months. Test restoration initially, annually and when IT infrastructure changes. | Low | High | High |
| Very Good | Business continuity and disaster recovery plans which are tested, documented and printed in hardcopy with a softcopy stored offline. Focus on the highest priority systems and data to recover. | Low | High | Medium |
| Very Good | System recovery capabilities e.g. virtualisation with snapshot backups, remotely installing operating systems and applications on computers, approved enterprise mobility, and onsite vendor support contracts. | Low | High | Medium |
| Mitigation Strategy Specific to Preventing Malicious Insiders: | ||||
| Very Good | Personnel management e.g. ongoing vetting especially for users with privileged access, immediately disable all accounts of departing users, and remind users of their security obligations and penalties. | |||
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