Microsoft Defender Antivirus relies on regularly updated security signatures, also called security intelligence, to recognize viruses, malware, spyware, ransomware, and other known threats. Windows normally downloads these updates automatically, but there are situations where you may want to check for a new update yourself.
For example, your PC may have been offline for several days, Windows Update may have been delayed, or Microsoft Defender may show an older security intelligence version.
In those situations, manually checking for an update can help make sure Defender has the latest available threat information.
Important Note: One important point for Windows 10 users is that Microsoft ended regular support for Windows 10 on October 14, 2025. That means standard Windows 10 users no longer receive free Windows Update security fixes, although some specialized Windows 10 editions and eligible Extended Security Updates arrangements can differ.
Update Windows Security Signatures Manually on Windows 11/10
- Open Windows Security from the Start menu.
- Select Virus & threat protection.
- Find Virus & threat protection updates.
- Select Check for updates.
- Allow Microsoft Defender to check for the latest security intelligence update.
- If an update is available, let Windows download and install it.
- Return to the same page and verify the Security intelligence version and update date.
Microsoft specifically recommends manually checking for new security intelligence from the Virus & threat protection area when you want to force a check for the latest Defender definitions.
Step 1: Open Windows Security
The first thing you need to do is open the Windows Security app. You do not need to search through multiple Control Panel windows to find the antivirus settings.
On Windows 11, select Start, type Windows Security, and select the matching result. On Windows 10, the same search method works. Windows Security provides access to Microsoft Defender Antivirus and other protection features on supported Windows installations.
If you cannot find it immediately, make sure you type the name correctly into the Start search box. Once the application opens, you should see several security areas, including Virus & threat protection, Firewall & network protection, and other security controls.
The exact appearance can vary slightly between Windows 11 and Windows 10, but the option you need is the same.
Start > Windows Security > Virus & threat protection
Step 2: Open Virus & Threat Protection
After Windows Security opens, select Virus & threat protection. This is the section that controls Microsoft Defender Antivirus scanning and threat protection.
Look for an area labeled Virus & threat protection updates. Depending on your Windows version and current Defender interface, the wording and placement can look slightly different.
This section contains information about when Defender last received security intelligence and gives you the option to check for a newer version.
Windows Security > Virus & threat protection > Virus & threat protection updates
Do not confuse a security intelligence update with a full Windows feature update. They serve different purposes. Security intelligence updates primarily provide Defender with current information it can use to identify known threats. Microsoft says these definitions can also be called signatures, DAT files, pattern files, identity files, or antivirus databases.
Step 3: Select Check for Updates
Now look for the Check for updates button under the Virus & threat protection updates section.
Select it to have Microsoft Defender check for newer security intelligence. If your PC already has the latest version, Windows should tell you that your protection is up to date. If a newer update is available, Windows will attempt to download and install it.
Virus & threat protection > Virus & threat protection updates > Check for updates
You may notice a short loading period while Windows checks Microsoft’s update service. The process can be quick, but the amount of time can vary depending on your internet connection and the update being downloaded.
You generally do not need to restart your PC just because Defender receives a security intelligence update. Microsoft notes that Defender security intelligence updates are among the updates that can install promptly rather than being held for a later Windows restart.
Step 4: Wait for the Security Intelligence Update to Finish
If Windows finds a newer Defender update, give it a moment to download and install. Keep your computer connected to the internet during this process.
You may see the status change while Windows processes the update. Avoid shutting down the computer in the middle of an update unless Windows specifically asks you to do so.
Once the process finishes, Windows Security should display updated information under Virus & threat protection updates.
Check for updates > Download or installation process > Wait for completion
If nothing happens after selecting the button, do not immediately assume that something is broken. Your Defender security intelligence may already be current, or Windows Update may be temporarily unable to communicate with Microsoft’s update servers.
Step 5: Verify the New Security Intelligence Version
After the update check finishes, take a moment to verify the information shown on the page.
Look for details such as the Security intelligence version, Engine version, and Last update information. The exact numbers will change regularly because Microsoft continually releases new threat intelligence.
This is a useful step if you are troubleshooting Defender or trying to confirm whether a manual update actually worked.
Windows Security > Virus & threat protection > Virus & threat protection updates > Security intelligence version
Do not worry if the version number you see in an older online article does not match the version on your computer. Security intelligence versions change frequently, so an older version number is not necessarily relevant to your current system.
Step 6: Try Windows Update if Defender Will Not Update
If Microsoft Defender refuses to download the latest security intelligence, the next thing to check is Windows Update.
On Windows 11, go to Start > Settings > Windows Update > Check for updates. On Windows 10, go to Start > Settings > Update & Security > Windows Update > Check for updates.
Windows normally handles Defender updates through its update infrastructure, so a problem with Windows Update can sometimes interfere with Defender updates as well. Microsoft recommends checking Windows Update when security software cannot update normally.
Start > Settings > Windows Update > Check for updates
Let Windows install any available updates that apply to your PC. Then return to Windows Security > Virus & threat protection and try Check for updates again.
Step 7: Run a Defender Scan After Updating
Once your security intelligence is current, you can run a scan if you were updating Defender because you suspected a security problem.
For a quick check, open Windows Security > Virus & threat protection > Quick scan. Microsoft also allows you to scan individual files or folders using Microsoft Defender. On Windows 11, you may need to select Show more options after right-clicking a file or folder before seeing the Defender scanning option.
Windows Security > Virus & threat protection > Quick scan
Updating the signatures does not itself scan your entire computer. It updates the threat information Defender uses, so running a scan afterward can be useful when you are investigating a suspicious download, application, or file.
What to Do If Windows Security Signatures Will Not Update
If the manual update continues to fail, start with the basics. Confirm that your computer has a working internet connection and make sure Windows Update is not showing an error.
You should also check whether another antivirus application is currently providing antivirus protection. Windows Security can show information about other security providers under its settings.
If Defender repeatedly reports update errors, Microsoft recommends trying to install the latest protection updates manually as part of its troubleshooting process.
Avoid downloading random Defender signature packages from third-party websites. When you need a manual update outside the normal Windows Security process, use Microsoft’s official update mechanisms rather than an unknown download site.
Faqs
What are Windows security signatures?
Windows security signatures are threat-identification information used by Microsoft Defender Antivirus. Microsoft also calls them security intelligence or definitions. They help Defender recognize known malware and other threats.
How often should I manually update Microsoft Defender?
You normally do not need to manually update it every day. Microsoft Defender is designed to receive security intelligence automatically. A manual check is useful when you want to confirm that the latest update is available or when automatic updating appears to have stopped working.
Do I need to restart Windows after updating Defender signatures?
Usually, a restart is not required simply because Microsoft Defender receives a security intelligence update. Microsoft identifies Defender security intelligence updates as updates that can install promptly.
Why does Microsoft Defender say my protection is out of date?
This can happen when Defender has not received recent security intelligence. It may also occur because of an internet connection problem, a Windows Update issue, or another problem affecting the update service. Start by selecting Check for updates in Windows Security.
Can I manually update Defender without Windows Security?
There are Microsoft-supported manual update methods for situations where normal updating is not working. However, for most home users, the simplest approach is Windows Security > Virus & threat protection > Check for updates. If that fails, troubleshoot Windows Update and Defender rather than relying on unofficial download websites.
Does updating security intelligence update Windows itself?
No. A security intelligence update is different from a Windows feature update or regular Windows quality update. Security intelligence primarily updates the information Microsoft Defender uses to identify threats.
Is Microsoft Defender automatically updated?
Yes. Microsoft says Defender automatically receives new security intelligence through Windows Update. You can also manually force a check from Virus & threat protection when needed.
Bottom Lines
Manually updating Windows security signatures is a simple way to check that Microsoft Defender Antivirus has current security intelligence. For most Windows 11 users, the process takes only a few clicks: Windows Security > Virus & threat protection > Virus & threat protection updates > Check for updates.
If the update succeeds, verify the Security intelligence version and the last update information. If it fails, check your internet connection and Windows Update before trying more advanced troubleshooting.
Keeping Defender’s security intelligence current is important because antivirus software needs current threat information to identify known malicious software.
Windows is designed to handle these updates automatically, so manual checking should generally be used as a troubleshooting or verification step rather than something you have to perform every day.