Can Windows Security remove ransomware?

Ransomware is a type of malicious software that encrypts files on a device and demands payment in order to decrypt them. It has become an increasingly common and disruptive threat. As ransomware attacks have proliferated, Windows users have looked to Windows Security, the built-in anti-malware software included in Windows operating systems, to protect against these attacks. But can Windows Security reliably detect, prevent, and remove ransomware?

How ransomware works

To understand whether Windows Security can deal with ransomware, it helps to first understand what ransomware is and how it operates. Ransomware is generally spread through phishing emails containing malicious attachments or links. If a user opens the attachment or clicks the link, the ransomware installer is downloaded onto their device. Once installed, the ransomware will silently encrypt files on the infected device, including documents, photos, videos, and other important data. Encrypting the files renders them inaccessible to the user.

Once the encryption is complete, the ransomware shows a ransom note demanding payment, usually in cryptocurrency like Bitcoin. The note claims that paying the ransom will decrypt the files. Newer ransomware strains may also threaten to delete files or publicly release them if payment isn’t received.

Built-in ransomware protection in Windows Security

To combat the rising threat of ransomware, Microsoft has added dedicated ransomware protection features to Windows Security in recent Windows versions. These are designed to both prevent ransomware infections and detect ransomware activity if an infection does occur. Some of the key capabilities include:

  • Controlled folder access – This feature lets users specify important folders like Documents, Pictures, etc. and restricts unauthorized apps from making changes to files in those folders. This prevents ransomware from encrypting files in protected folders.
  • Attack surface reduction rules – These are rules that block known ransomware behavior patterns and tampering techniques. For example, rules can block suspicious programs from launching and stop untrusted processes from modifying files.
  • Next gen protection – This uses advanced machine learning algorithms to detect and block new ransomware variants based on their behavior, even if the ransomware is not yet known.
  • Ransomware detection notifications – Windows Security will display a prominent notification if ransomware activity is detected, allowing users to take action.

These capabilities provide protection against common ransomware attack vectors. However, Windows Security may struggle to block more sophisticated, zero-day ransomware threats that find ways around Microsoft’s detection mechanisms.

What happens if ransomware infects your device?

If ransomware is able to bypass Windows Security and encrypt files, Windows Security will still attempt to detect the active attack. It scans for the telltale changes that ransomware makes, like file encryption, replacement of original files with encrypted copies, changes to file extensions, etc.

If evidence of ransomware is found, Windows Security will:

  • Display a ransomware detection alert
  • Stop the ransomware process from running
  • Attempt to delete or quarantine the ransomware
  • Block the ransomware from further modification of files

These actions prevent any additional damage from occurring and may successfully remove the ransomware. However, Windows Security cannot automatically decrypt any files already encrypted prior to detection.

Does Windows Security decrypt ransomware-encrypted files?

Unfortunately, Windows Security does not have built-in decryption capabilities to recover files encrypted by ransomware. The ransomware uses cryptographically strong encryption algorithms that are virtually impossible to break without the decryption key.

While Windows Security tries to detect and stop ransomware, once your files are encrypted, removing the ransomware does not decrypt them. The only way to reliably decrypt most ransomware attacks is with the private key or decryptor from the attackers after paying the ransom.

Of course, there is no guarantee the criminals will provide working decryption even if paid. Paying ransoms also funds and incentivizes more ransomware crime.

When decryption is possible without the ransomware creators

In some rare cases, security researchers are able to find flaws in the ransomware’s encryption implementation that allow files to be recovered without the attacker’s private key. This generally only occurs with new or amateurish ransomware variants. Researchers may also eventually crack the encryption of older ransomware strains as computing power increases over time.

For common ransomware families like Ryuk, WannaCry, NotPetya, etc. though, viable decryption methods without paying the ransom are extremely unlikely to surface.

Strengths of Windows Security against ransomware

While Windows Security ultimately cannot decrypt files post-encryption, it still provides meaningful ransomware protections through preventative measures. Strengths include:

  • Real-time protection blocks many ransomware execution attempts
  • Rules to block ransomware behavior patterns slow down infections
  • Secure Folder access prevents encryption of files in key folders like Documents and Pictures
  • Cloud backups via OneDrive allow recovering encrypted files from the cloud
  • Notifications alert users about ransomware detection early on

These protections are adequate for defending against common and mass-distributed ransomware attacks. However, Windows Security may falter against more advanced threats like targeted ransomware aimed at businesses.

Weaknesses of Windows Security against ransomware

The core weakness of Windows Security’s ransomware protection is that it cannot decrypt files after an infection occurs. Additional weaknesses include:

  • Signature-based detection can miss new ransomware variants
  • User-dependent features like Controlled Folder Access rely on proper configuration
  • Advanced attacks like Ryuk can disable Windows Security
  • Not all folders may be protected by Controlled Folder Access
  • Notifications don’t guarantee users will take action in time

Due to these gaps, sophisticated ransomware campaigns often succeed in encrypting files before Windows Security can respond. And once encryption occurs, the built-in protections offer no native decryption capability.

Third-party ransomware removal and decryption tools

Because Windows Security cannot directly decrypt files, third-party utilities have emerged that offer ransomware removal with limited decryption in some cases. Examples include:

  • Malwarebytes Anti-Ransomware – Detects and blocks ransomware using behavior analysis. May decrypt files if ransomware fails to completely overwrite originals.
  • Avast Ransomware Decryption Tools – Occasionally releases free decryption keys and tools for specific ransomware families like GandCrab and Locky. Allows infected users to decrypt files without paying.
  • Emsisoft Decrypter – Works to recover decryption keys from memory to unlock files after infections by supported ransomware strains.

However, these tools still have significant limitations. They typically only work if the ransomware is poorly designed or uses reversible encryption. The most dangerous ransomware tends to use cryptographically sound encryption that cannot be easily reversed even with third-party tools.

Should you rely solely on Windows Security for ransomware protection?

Windows Security provides a decent baseline of ransomware defenses that can block common consumer ransomware threats. However, organizations and high-value targets may want to deploy additional safeguards. Some best practices include:

  • Enable all Windows Security ransomware protections
  • Use software restriction policies to block untrusted programs
  • Implement least privilege access controls
  • Backup critical files to disconnected external drives
  • Install additional anti-ransomware software like Malwarebytes
  • Educate employees on ransomware prevention and response
  • Simulate ransomware attacks to test defenses

Following strict cybersecurity practices like these is essential for reducing the risk of ransomware breaching defenses and encrypting critical files and systems.


Windows Security provides started protections that can block common consumer ransomware threats like Locky and Cerber. However, sophisticated ransomware like Ryuk often evades Windows Security’s defenses and encrypts files. Once encryption occurs, Windows Security cannot natively decrypt the impacted files without the attacker’s decryption key.

While removal of the ransomware binary may stop further damage, Windows Security does not have built-in capabilities to recover encrypted files. This core limitation means organizations with valuable data should not rely solely on Windows Security and should implement layered ransomware defenses. Individuals can benefit from Windows Security but should still take precautions like offline backups. Promptly removing detected ransomware combined with other best practices provides the best chance of avoiding paying ransoms and recovering from attacks.

Ransomware Protection Feature Effectiveness
Real-time protection Highly effective against known ransomware
Controlled folder access Useful IF properly configured by user
Attack surface reduction rules Helps block common behaviors
Ransomware behavior detection Detects active encryption in progress
Decryption capabilities None inherent; No help after encryption