The easiest
method to ensure that an ActiveX object is not executed within IE is to set a kill bit on the
CLSID value. The kill bit on the ActiveX??™s CLSID value will ensure the control is not
called by IE. However, if other settings contradict the kill bit, such as SFS or SFI controls,
and are not marked safe, then the kill bit would not be used.
To ensure an ActiveX control is not called by IE with the use of kill bit, complete the
following steps:
1. Open the registry editor by choosing Start | Run | Regedit.
2. Browse to the appropriate CLSID of the ActiveX object: HKEY_LOCAL_
MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\
{
}
208 Hacking Exposed Web 2.0
3. Expand the CLSID key, which will show a DWORD value called Compatibility
Flags, as shown in Figure 8-3.
4. In order to set the kill bit, double-click the Compatibility Flag and change the
current value for Value data to 400 (0x00000400).
You have now set the kill bit for the ActiveX object.
Buffer Over?¬‚ ows in ActiveX Objects
Buffer overflows are common in ActiveX, primarily because inputs are not being checked
and validated in the control before input is accepted.
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