Windows operating system security

Security and privacy depend on an operating system that guards your system and information from the moment it starts up, providing fundamental chip-to-cloud protection. Windows 11 is the most secure Windows yet with extensive security measures designed to help keep you safe. These measures include built-in advanced encryption and data protection, robust network and system security, and intelligent safeguards against ever-evolving threats.

Watch the latest Microsoft Mechanics Windows 11 security video that shows off some of the latest Windows 11 security technology.

Use the links in the following sections to learn more about the operating system security features and capabilities in Windows.

System security

Feature name Description
Secure Boot and Trusted Boot Secure Boot and Trusted Boot help to prevent malware and corrupted components from loading when a device starts.

Secure Boot starts with initial boot-up protection, and then Trusted Boot picks up the process. Together, Secure Boot and Trusted Boot help to ensure the system boots up safely and securely.
Measured boot Measured Boot measures all important code and configuration settings during the boot of Windows. This includes: the firmware, boot manager, hypervisor, kernel, secure kernel and operating system. Measured Boot stores the measurements in the TPM on the machine, and makes them available in a log that can be tested remotely to verify the boot state of the client.

The Measured Boot feature provides anti-malware software with a trusted (resistant to spoofing and tampering) log of all boot components that started before it. The anti-malware software can use the log to determine whether components that ran before it are trustworthy, or if they're infected with malware. The anti-malware software on the local machine can send the log to a remote server for evaluation. The remote server may initiate remediation actions, either by interacting with software on the client, or through out-of-band mechanisms, as appropriate.
Device health attestation service The Windows device health attestation process supports a zero-trust paradigm that shifts the focus from static, network-based perimeters, to users, assets, and resources. The attestation process confirms the device, firmware, and boot process are in a good state and haven't been tampered with before they can access corporate resources. The determinations are made with data stored in the TPM, which provides a secure root of trust. The information is sent to an attestation service, such as Azure Attestation, to verify the device is in a trusted state. Then, an MDM tool like Microsoft Intune reviews device health and connects this information with Microsoft Entra ID for conditional access.
Windows security policy settings and auditing Microsoft provides a robust set of security settings policies that IT administrators can use to protect Windows devices and other resources in their organization.
Assigned Access (kiosk mode) Some desktop devices in an enterprise serve a special purpose. For example, a PC in the lobby that customers use to see your product catalog. Or, a PC displaying visual content as a digital sign. Windows client offers two different locked-down experiences for public or specialized use: A single-app kiosk that runs a single Universal Windows Platform (UWP) app in full screen above the lock screen, or A multi-app kiosk that runs one or more apps from the desktop.

Kiosk configurations are based on Assigned Access, a feature in Windows that allows an administrator to manage the user's experience by limiting the application entry points exposed to the user.

Virus and threat protection

Feature name Description
Microsoft Defender Antivirus Microsoft Defender Antivirus is a protection solution included in all versions of Windows. From the moment you boot Windows, Microsoft Defender Antivirus continually monitors for malware, viruses, and security threats. Updates are downloaded automatically to help keep your device safe and protect it from threats. Microsoft Defender Antivirus includes real-time, behavior-based, and heuristic antivirus protection.

The combination of always-on content scanning, file and process behavior monitoring, and other heuristics effectively prevents security threats. Microsoft Defender Antivirus continually scans for malware and threats and also detects and blocks potentially unwanted applications (PUA) which are applications that are deemed to negatively impact your device but aren't considered malware.
Local Security Authority (LSA) Protection Windows has several critical processes to verify a user's identity. Verification processes include Local Security Authority (LSA), which is responsible for authenticating users and verifying Windows logins. LSA handles tokens and credentials such as passwords that are used for single sign-on to a Microsoft account and Azure services. To help protect these credentials, additional LSA protection only allows loading of trusted, signed code and provides significant protection against Credential theft.

LSA protection is enabled by default on new, enterprise joined Windows 11 devices with added support for non-UEFI lock and policy management controls via MDM and group policy.
Attack surface reduction (ASR) Attack surface reduction (ASR) rules help to prevent software behaviors that are often abused to compromise your device or network. By reducing the number of attack surfaces, you can reduce the overall vulnerability of your organization.

Administrators can configure specific ASR rules to help block certain behaviors, such as launching executable files and scripts that attempt to download or run files, running obfuscated or otherwise suspicious scripts, performing behaviors that apps don't usually initiate during normal day-to-day work.
Tamper protection settings for MDE Tamper protection is a capability in Microsoft Defender for Endpoint that helps protect certain security settings, such as virus and threat protection, from being disabled or changed. During some kinds of cyber attacks, bad actors try to disable security features on devices. Disabling security features provides bad actors with easier access to your data, the ability to install malware, and the ability to exploit your data, identity, and devices. Tamper protection helps guard against these types of activities.
Controlled folder access You can protect your valuable information in specific folders by managing app access to specific folders. Only trusted apps can access protected folders, which are specified when controlled folder access is configured. Commonly used folders, such as those used for documents, pictures, downloads, are typically included in the list of controlled folders. Controlled folder access works with a list of trusted apps. Apps that are included in the list of trusted software work as expected. Apps that aren't included in the trusted list are prevented from making any changes to files inside protected folders.

Controlled folder access helps to protect user's valuable data from malicious apps and threats, such as ransomware.
Exploit protection Exploit protection automatically applies several exploit mitigation techniques to operating system processes and apps. Exploit protection works best with Microsoft Defender for Endpoint, which gives organizations detailed reporting into exploit protection events and blocks as part of typical alert investigation scenarios. You can enable exploit protection on an individual device, and then use MDM or group policy to distribute the configuration file to multiple devices. When a mitigation is encountered on the device, a notification will be displayed from the Action Center. You can customize the notification with your company details and contact information. You can also enable the rules individually to customize which techniques the feature monitors.
Microsoft Defender SmartScreen Microsoft Defender SmartScreen protects against phishing, malware websites and applications, and the downloading of potentially malicious files. For enhanced phishing protection, SmartScreen also alerts people when they're entering their credentials into a potentially risky location. IT can customize which notifications appear via MDM or group policy. The protection runs in audit mode by default, giving IT admins full control to make decisions around policy creation and enforcement.
Microsoft Defender for Endpoint Microsoft Defender for Endpoint is an enterprise endpoint detection and response solution that helps security teams to detect, investigate, and respond to advanced threats. Organizations can use the rich event data and attack insights Defender for Endpoint provides to investigate incidents. Defender for Endpoint brings together the following elements to provide a more complete picture of security incidents: endpoint behavioral sensors, cloud security analytics, threat intelligence and rich response capabilities.

Network security

Feature name Description
Transport Layer Security (TLS) Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a network. TLS 1.3 is the latest version of the protocol and is enabled by default in Windows 11. This version eliminates obsolete cryptographic algorithms, enhances security over older versions, and aims to encrypt as much of the TLS handshake as possible. The handshake is more performant with one fewer round trip per connection on average, and supports only five strong cipher suites which provide perfect forward secrecy and less operational risk.
Domain Name System (DNS) security Starting in Windows 11, the Windows DNS client supports DNS over HTTPS (DoH), an encrypted DNS protocol. This allows administrators to ensure their devices protect DNS queries from on-path attackers, whether they're passive observers logging browsing behavior or active attackers trying to redirect clients to malicious sites.

In a zero-trust model where there is no trust placed in a network boundary, having a secure connection to a trusted name resolver is required.
Bluetooth pairing and connection protection The number of Bluetooth devices connected to Windows continues to increase. Windows supports all standard Bluetooth pairing protocols, including classic and LE Secure connections, secure simple pairing, and classic and LE legacy pairing. Windows also implements host based LE privacy. Windows updates help users stay current with OS and driver security features in accordance with the Bluetooth Special Interest Group (SIG), Standard Vulnerability Reports, and issues beyond those required by the Bluetooth core industry standards. Microsoft strongly recommends that users ensure their firmware and/ or software of their Bluetooth accessories are kept up to date.
WiFi Security Wi-Fi Protected Access (WPA) is a security certification program designed to secure wireless networks. WPA3 is the latest version of the certification and provides a more secure and reliable connection method as compared to WPA2 and older security protocols. Windows supports three WPA3 modes: WPA3 personal with the Hash-to-Element (H2E) protocol, WPA3 Enterprise, and WPA3 Enterprise 192-bit Suite B.

Windows 11 also supports WFA defined WPA3 Enterprise that includes enhanced Server Cert validation and TLS 1.3 for authentication using EAP-TLS Authentication.
Opportunistic Wireless Encryption (OWE) Opportunistic Wireless Encryption (OWE) is a technology that allows wireless devices to establish encrypted connections to public Wi-Fi hotspots.
Windows Firewall Windows Firewall provides host-based, two-way network traffic filtering, blocking unauthorized traffic flowing into or out of the local device based on the types of networks to which the device is connected. Windows Firewall reduces the attack surface of a device with rules to restrict or allow traffic by many properties such as IP addresses, ports, or program paths. Reducing the attack surface of a device increases manageability and decreases the likelihood of a successful attack.

With its integration with Internet Protocol Security (IPsec), Windows Firewall provides a simple way to enforce authenticated, end-to-end network communications. It provides scalable, tiered access to trusted network resources, helping to enforce integrity of the data, and optionally helping to protect the confidentiality of the data. Windows Firewall is a host-based firewall that is included with the operating system, there's no additional hardware or software required. Windows Firewall is also designed to complement existing non-Microsoft network security solutions through a documented application programming interface (API).
Virtual private network (VPN) The Windows VPN client platform includes built in VPN protocols, configuration support, a common VPN user interface, and programming support for custom VPN protocols. VPN apps are available in the Microsoft Store for both enterprise and consumer VPNs, including apps for the most popular enterprise VPN gateways.

In Windows 11, the most commonly used VPN controls are integrated right into the Quick Actions pane. From the Quick Actions pane, users can see the status of their VPN, start and stop the VPN tunnels, and access the Settings app for more controls.
Always On VPN (device tunnel) With Always On VPN, you can create a dedicated VPN profile for the device. Unlike User Tunnel, which only connects after a user logs on to the device, Device Tunnel allows the VPN to establish connectivity before a user sign-in. Both Device Tunnel and User Tunnel operate independently with their VPN profiles, can be connected at the same time, and can use different authentication methods and other VPN configuration settings as appropriate.
Direct Access DirectAccess allows connectivity for remote users to organization network resources without the need for traditional Virtual Private Network (VPN) connections.

With DirectAccess connections, remote devices are always connected to the organization and there's no need for remote users to start and stop connections.
Server Message Block (SMB) file service SMB Encryption provides end-to-end encryption of SMB data and protects data from eavesdropping occurrences on internal networks. In Windows 11, the SMB protocol has significant security updates, including AES-256 bits encryption, accelerated SMB signing, Remote Directory Memory Access (RDMA) network encryption, and SMB over QUIC for untrusted networks. Windows 11 introduces AES-256-GCM and AES-256-CCM cryptographic suites for SMB 3.1.1 encryption. Windows administrators can mandate the use of more advanced security or continue to use the more compatible, and still-safe, AES-128 encryption.
Server Message Block Direct (SMB Direct) SMB Direct (SMB over remote direct memory access) is a storage protocol that enables direct memory-to-memory data transfers between device and storage, with minimal CPU usage, while using standard RDMA-capable network adapters.

SMB Direct supports encryption, and now you can operate with the same safety as traditional TCP and the performance of RDMA. Previously, enabling SMB encryption disabled direct data placement, making RDMA as slow as TCP. Now data is encrypted before placement, leading to relatively minor performance degradation while adding AES-128 and AES-256 protected packet privacy.

Encryption and data protection

Feature name Description
BitLocker management The BitLocker CSP allows an MDM solution, like Microsoft Intune, to manage the BitLocker encryption features on Windows devices. This includes OS volumes, fixed drives and removeable storage, and recovery key management into Microsoft Entra ID.
BitLocker enablement BitLocker Drive Encryption is a data protection feature that integrates with the operating system and addresses the threats of data theft or exposure from lost, stolen, or inappropriately decommissioned computers. BitLocker uses AES algorithm in XTS or CBC mode of operation with 128-bit or 256-bit key length to encrypt data on the volume. Cloud storage on Microsoft OneDrive or Azure can be used to save recovery key content. BitLocker can be managed by any MDM solution such as Microsoft Intune, using a configuration service provider (CSP).

BitLocker provides encryption for the OS, fixed data, and removable data drives leveraging technologies like hardware security test interface (HSTI), Modern Standby, UEFI Secure Boot and TPM.
Encrypted hard drive Encrypted hard drives are a class of hard drives that are self-encrypted at the hardware level and allow for full disk hardware encryption while being transparent to the device user. These drives combine the security and management benefits provided by BitLocker Drive Encryption with the power of self-encrypting drives.

By offloading the cryptographic operations to hardware, encrypted hard drives increase BitLocker performance and reduce CPU usage and power consumption. Because encrypted hard drives encrypt data quickly, BitLocker deployment can be expanded across enterprise devices with little to no impact on productivity.
Personal data encryption (PDE) Personal data encryption (PDE) works with BitLocker and Windows Hello for Business to further protect user documents and other files, including when the device is turned on and locked. Files are encrypted automatically and seamlessly to give users more security without interrupting their workflow.

Windows Hello for Business is used to protect the container, which houses the encryption keys used by PDE. When the user signs in, the container gets authenticated to release the keys in the container to decrypt user content.
Email Encryption (S/MIME) Email encryption enables users to encrypt outgoing email messages and attachments, so only intended recipients with a digital ID (certificate) can read them. Users can digitally sign a message, which verifies the identity of the sender and confirms the message hasn't been tampered with. The encrypted messages can be sent by a user to other users within their organization or external contacts if they have proper encryption certificates.