System Service Dispatch Table

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The System Service Descriptor Table (SSDT) is an internal dispatch table within Microsoft Windows.

Hooking SSDT calls is often used as a technique in both Windows rootkits and antivirus software.[1][2]

In 2010, many computer security products which relied on hooking SSDT calls were shown to be vulnerable to exploits using race conditions to attack the products' security checks.[2]

Structure of the SSDT[edit]

    PULONG ServiceTableBase; 
    PULONG ServiceCounterTableBase; 
    ULONG NumberOfServices; 
    PUCHAR ParamTableBase; 

The pointer to this structure is KeServiceDescriptorTable, exported by ntoskrnl.exe.