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What is the Kill-Bit?

April 26, 2017kill-bit

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What is the Kill-Bit?

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The Kill-Bit (a.k.a. “killbit”) is not actually a bit. The Kill-Bit is a registry entry for a particular CLSID that marks the COM object / ActiveX control referenced by that CLSID as non-loadable in the browser and other scriptable environments. Microsoft releases Kill-Bits in security updates to block vulnerable ActiveX controls and COM objects which are vulnerable to security flaws when hosted in the browser. Issuing a Kill-Bit for the control marks that particular control as forbidden to instantiate in the browser. Issue a Kill-Bit by setting the Compatibility Flags value to 0x400 for a control in the registry as described in KB Article 240797.