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Desktop apps
Smooth
Farm-fresh
virus, Protection
Black
32x32
Glyph
16x16 Free Toolbar Icons
protect, Antivirus, yellow
Khaki
16x16
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Ginux
Protection, shield, security
DimGray
64x64
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3D
Free Applications Icons
Protection, secured, private
24x24
Unlocked, password, Protection
One bit
Protection, shield, Antivirus
Teal
48x48