Update Microsoft antimalware and antispyware software

You can update your Microsoft security software by downloading the definitions on this page.

A definition is how we clean or remove a virus or other threat from your computer. When you update your definitions, you are updating your protection against threats.

You must have Microsoft security software installed to use these definitions.

How to get updates for Microsoft security products

There are two ways for you to receive definition updates.

You can update your definitions by going to Windows Update or clicking the Update button within the Update tab of your Microsoft security software.

Screenshot of the Update tab on Microsoft security software

These definitions are updated once every 24 hours.

Sometimes you might want to update more often than once a day. This can be especially helpful if a particular piece of malware just won’t go away, no matter how many times your software tries to clean it.

You can get the latest updates by coming directly to this page.

Latest definitions

Antimalware and antispyware definitions

For antimalware and antispyware, the latest versions are: 1.157.1384.0, Sep 07, 2013 01:20 AM UTC

Use this table to download the right definitions for your computer.

Download either the 32-bit or 64-bit version depending on your version of Windows and the security software you have installed.

To find out your version of Windows:

Open the Start menu or Start screen, type Computer, and press Enter.
On the left side of the File Explorer window that appears, right-click or tap and hold Computer, and then click or tap Properties.

Your version will be shown under System type.

You can find out more about our products on the Microsoft security software page.
Antivirus and antispyware definitions (choose either 32-bit or 64-bit depending on your computer)

Microsoft Security Essentials	32-bit \| 64-bit
Windows Defender in Windows 8	32-bit \| 64-bit \| ARM
Windows Defender in Windows XP through 7	32-bit \| 64-bit
Microsoft Diagnostics and Recovery Toolset (DaRT)	32-bit \| 64-bit
Forefront Client Security	32-bit \| 64-bit
Forefront Server Security	32-bit \| 64-bit
Forefront Endpoint Protection	Visit this link
System Center 2012 Configuration Manager	Visit this link
System Center 2012 Endpoint Protection	Visit this link
Windows Intune	Visit this link

Network Inspection System definitions

You can also download Network Inspection System (NIS) definitions for Microsoft Security Essentials,Forefront Endpoint Protection, and System Center 2012 Endpoint Protection. These definitions are designed to protect you from exploits and network infections.

The version of your Microsoft security software determines which type of NIS definitions you must download.

To determine your version:

Open your security software by double clicking on the icon in the system tray (you may need to click the arrow to see the icon) or, in Windows 8, search for Windows Defender:
Click the arrow next to Help and choose About <Software name>:
Your software version number is displayed at the line labelled Antimalware Client Version