How to protect networks Individuals, and small and medium-sized businesses ■ Update devices and systems – update software and turn on automatic operating system updates. ■ Have a cyber incident response plan in place and apply appropriate cyber security measures proportionate to the risk of compromise. Government, large organisations and infrastructure Know the networks and the security risks: ■ The ACSC encourages all users to review their networks to establish where their most valuable and sensitive information lies, and understand their risks. ■ Have a cyber incident response plan in place and apply appropriate cyber security measures proportionate to the risk of compromise. Prioritise patching within 48 hours of a patch release: ■ Adversaries use automated tools to regularly scan for and exploit network vulnerabilities, often within 24 to 48 hours of public reporting of a vulnerability. ■ This means that where an exploit exists, organisations should prioritise patching within 48 hours of a patch release to protect their networks from malicious activity. Follow ACSC advice: ■ System patching ■ Implement network segmentation and segregation ■ Operating system hardening ■ Web shell malware ■ Web Shells – Threat Awareness and Guidance Stay updated The ACSC regularly updates advice on known vulnerabilities as well as the detection, prevention and mitigation of malicious activity: ■ ACSC Alerts ■ ACSC Advisories ■ Advisory 2021–002: Active exploitation of Microsoft Exchange servers 40