The WMI allow you to get the installed Antivirus, AntiSpyware and Firewall (third party)  software using the root\SecurityCenter or the root\SecurityCenter2 namespaces and the AntiVirusProduct , AntiSpywareProduct, FirewallProduct classes.

First you must know which these classes and namespaces are not documented by Microsoft and only are supported in Windows Desktops editions (Windows XP, Windows Vista and Windows 7).
Now depending of the Windows version the properties retrieved by the the same class can change. this is a summary of the classes and properties availables depending of the windows version

Windows XP

Namespace : SecurityCenter
Classes availables: AntiVirusProduct, FirewallProduct

AntiVirusProduct-Properties

• companyName
• displayName
• enableOnAccessUIMd5Hash
• enableOnAccessUIParameters
• instanceGuid
• onAccessScanningEnabled
• pathToEnableOnAccessUI
• pathToUpdateUI
• productUptoDate
• updateUIMd5Hash
• updateUIParameters
• versionNumber

FirewallProduct-Properties

• companyName
• displayName
• enabled
• enableUIMd5Hash
• enableUIParameters
• instanceGuid
• pathToEnableUI
• versionNumber

Windows Vista and Windows 7

Namespace : SecurityCenter2
Classes availables : AntiVirusProduct, AntiSpywareProduct, FirewallProduct

AntiVirusProduct, AntiSpywareProduct, FirewallProduct – Properties

• displayName
• instanceGuid
• pathToSignedProductExe
• pathToSignedReportingExe
• productState

This is a sample project which determine the Antivirus, AntiSpyware and Firewall software installed in the system.

program GetSecurityCenterInfo;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  Windows,
  ActiveX,
  ComObj,
  Variants;

type
  TSecurityCenterProduct = (AntiVirusProduct,AntiSpywareProduct,FirewallProduct);
const
  WmiRoot='root';
  WmiClassSCProduct     : array [TSecurityCenterProduct] of string = ('AntiVirusProduct','AntiSpywareProduct','FirewallProduct');
  WmiNamespaceSCProduct : array [Boolean] of string = ('SecurityCenter','SecurityCenter2');

function VerSetConditionMask(dwlConditionMask: int64;dwTypeBitMask: DWORD; dwConditionMask: Byte): int64; stdcall; external kernel32;

{$IFDEF UNICODE}
function VerifyVersionInfo(var LPOSVERSIONINFOEX : OSVERSIONINFOEX;dwTypeMask: DWORD;dwlConditionMask: int64): BOOL; stdcall; external kernel32 name 'VerifyVersionInfoW';
{$ELSE}
function VerifyVersionInfo(var LPOSVERSIONINFOEX : OSVERSIONINFOEX;dwTypeMask: DWORD;dwlConditionMask: int64): BOOL; stdcall; external kernel32 name 'VerifyVersionInfoA';
{$ENDIF}

//verifies that the application is running on Windows 2000 Server or a later server, such as Windows Server 2003 or Windows Server 2008.
function Is_Win_Server : Boolean;
const
   VER_NT_SERVER      = $0000003;
   VER_EQUAL          = 1;
   VER_GREATER_EQUAL  = 3;
var
   osvi             : OSVERSIONINFOEX;
   dwlConditionMask : DWORDLONG;
   op               : Integer;
begin
   dwlConditionMask := 0;
   op:=VER_GREATER_EQUAL;

   ZeroMemory(@osvi, sizeof(OSVERSIONINFOEX));
   osvi.dwOSVersionInfoSize := sizeof(OSVERSIONINFOEX);
   osvi.dwMajorVersion := 5;
   osvi.dwMinorVersion := 0;
   osvi.wServicePackMajor := 0;
   osvi.wServicePackMinor := 0;
   osvi.wProductType := VER_NT_SERVER;

   dwlConditionMask:=VerSetConditionMask( dwlConditionMask, VER_MAJORVERSION, op );
   dwlConditionMask:=VerSetConditionMask( dwlConditionMask, VER_MINORVERSION, op );
   dwlConditionMask:=VerSetConditionMask( dwlConditionMask, VER_SERVICEPACKMAJOR, op );
   dwlConditionMask:=VerSetConditionMask( dwlConditionMask, VER_SERVICEPACKMINOR, op );
   dwlConditionMask:=VerSetConditionMask( dwlConditionMask, VER_PRODUCT_TYPE, VER_EQUAL );

   Result:=VerifyVersionInfo(osvi,VER_MAJORVERSION OR VER_MINORVERSION OR
      VER_SERVICEPACKMAJOR OR VER_SERVICEPACKMINOR OR VER_PRODUCT_TYPE, dwlConditionMask);
end;

procedure  GetSCProductInfo(SCProduct:TSecurityCenterProduct);
var
  FSWbemLocator : OLEVariant;
  FWMIService   : OLEVariant;
  FWbemObjectSet: OLEVariant;
  FWbemObject   : OLEVariant;
  oEnum         : IEnumvariant;
  iValue        : LongWord;
  osVerInfo     : TOSVersionInfo;
begin
  osVerInfo.dwOSVersionInfoSize:=SizeOf(TOSVersionInfo);
  GetVersionEx(osVerInfo);
  if (SCProduct=AntiSpywareProduct) and (osVerInfo.dwMajorVersion<6)  then exit;   FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');   FWMIService   := FSWbemLocator.ConnectServer('localhost',Format('%s\%s',[WmiRoot,WmiNamespaceSCProduct[osVerInfo.dwMajorVersion>=6]]), '', '');
  FWbemObjectSet:= FWMIService.ExecQuery(Format('SELECT * FROM %s',[WmiClassSCProduct[SCProduct]]),'WQL',0);
  oEnum         := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  while oEnum.Next(1, FWbemObject, iValue) = 0 do
  begin
    if osVerInfo.dwMajorVersion>=6 then  //windows vista or newer
    begin
      Writeln(Format('displayName                    %s',[FWbemObject.displayName]));// String
      Writeln(Format('instanceGuid                   %s',[FWbemObject.instanceGuid]));// String
      Writeln(Format('pathToSignedProductExe         %s',[FWbemObject.pathToSignedProductExe]));// String
      Writeln(Format('pathToSignedReportingExe       %s',[FWbemObject.pathToSignedReportingExe]));// String
      Writeln(Format('productState                   %s',[FWbemObject.productState]));// Uint32
    end
    else
    begin
     case SCProduct of

        AntiVirusProduct :
         begin
            Writeln(Format('companyName                    %s',[FWbemObject.companyName]));// String
            Writeln(Format('displayName                    %s',[FWbemObject.displayName]));// String
            Writeln(Format('enableOnAccessUIMd5Hash        %s',[FWbemObject.enableOnAccessUIMd5Hash]));// Uint8
            Writeln(Format('enableOnAccessUIParameters     %s',[FWbemObject.enableOnAccessUIParameters]));// String
            Writeln(Format('instanceGuid                   %s',[FWbemObject.instanceGuid]));// String
            Writeln(Format('onAccessScanningEnabled        %s',[FWbemObject.onAccessScanningEnabled]));// Boolean
            Writeln(Format('pathToEnableOnAccessUI         %s',[FWbemObject.pathToEnableOnAccessUI]));// String
            Writeln(Format('pathToUpdateUI                 %s',[FWbemObject.pathToUpdateUI]));// String
            Writeln(Format('productUptoDate                %s',[FWbemObject.productUptoDate]));// Boolean
            Writeln(Format('updateUIMd5Hash                %s',[FWbemObject.updateUIMd5Hash]));// Uint8
            Writeln(Format('updateUIParameters             %s',[FWbemObject.updateUIParameters]));// String
            Writeln(Format('versionNumber                  %s',[FWbemObject.versionNumber]));// String
         end;

       FirewallProduct  :
         begin
            Writeln(Format('companyName                    %s',[FWbemObject.companyName]));// String
            Writeln(Format('displayName                    %s',[FWbemObject.displayName]));// String
            Writeln(Format('enabled                        %s',[FWbemObject.enabled]));// Boolean
            Writeln(Format('enableUIMd5Hash                %s',[FWbemObject.enableUIMd5Hash]));// Uint8
            Writeln(Format('enableUIParameters             %s',[FWbemObject.enableUIParameters]));// String
            Writeln(Format('instanceGuid                   %s',[FWbemObject.instanceGuid]));// String
            Writeln(Format('pathToEnableUI                 %s',[FWbemObject.pathToEnableUI]));// String
            Writeln(Format('versionNumber                  %s',[FWbemObject.versionNumber]));// String
         end;
     end;
    end;
    Writeln('');
    FWbemObject:=Unassigned;
  end;
end;

begin
 try
    if Is_Win_Server then
    begin
     Writeln('Sorry this app only can run in desktop operating systems.');
     Halt;
    end;

    CoInitialize(nil);
    try
      Writeln('AntiVirus Info');
      Writeln('--------------');
      GetSCProductInfo(AntiVirusProduct);
      Writeln('AntiSpyware Info');
      Writeln('----------------');
      GetSCProductInfo(AntiSpywareProduct);
      Writeln('Firewall Info');
      Writeln('-------------');
      GetSCProductInfo(FirewallProduct);
      Readln;
    finally
      CoUninitialize;
    end;
 except
    on E:Exception do
    begin
        Writeln(E.Classname, ':', E.Message);
        Readln;
    end;
  end;
end.

And here is the result of the app.