Antivirus Definition

NORTON 2014 Definition

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Download Norton 2014  Latest Definition

Microsoft Security Software Definition

Direct links:
Microsoft Security Essentials Update for 32 bit Latest Definition
Microsoft Security Essentials Update for 64 bit Latest Definition

Windows Defender in Windows 8 Update for 32 bit Latest Definition
Windows Defender in Windows 8 Update for 64 bit Latest Definition
Windows Defender in Windows 8 Update for ARM Latest Definition

AVG Definition Updates:

Direct link: Download AVG Latest Definition