Stricter Microsoft Defender rules will improve security on Windows 11 computers from 2 November 2026

Microsoft Defender’s Attack Surface Reduction (ASR) rules improve security by restricting the activities of applications deemed to pose a risk. The rules provide an additional layer of protection alongside traditional antivirus software by blocking techniques commonly used by attackers and malware.

The settings will be enabled in the background, and you will not receive a separate notification on your computer.

The change in brief

• ASR rules can, for example, prevent suspicious scripts from running, block processes launched by Office applications and stop techniques used to steal login credentials.
• Microsoft Defender is a suite of Microsoft security solutions that protects devices, user accounts, email, applications and cloud services against cyber threats and helps detect and respond to threats.
• Some applications or files you use may be blocked mistakenly (false positive). In some cases, you will receive a notification advising you to contact support (Helpdesk). However, you may not receive a separate notification in every case.
• If an application or file you use is blocked erroneously, please contact IT Helpdesk:
  
  • Chat (weekdays 9 AM to 3 PM, chatbot 24/7): helsinki.fi/helpdesk
  • Call: 029 41 55555 (weekdays 9 AM to 3 PM, local network charge / mobile call charge)
  • E-mail: helpdesk@helsinki.fi