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• [GEEK SCHOOL] Network Security 2: Preventing Disaster with User Account Control

  - by Ciprian Rusen

  In this second lesson in our How-To Geek School about securing the Windows devices in your network, we will talk about User Account Control (UAC). Users encounter this feature each time they need to install desktop applications in Windows, when some applications need administrator permissions in order to work and when they have to change different system settings and files. UAC was introduced in Windows Vista as part of Microsoft’s “Trustworthy Computing” initiative. Basically, UAC is meant to act as a wedge between you and installing applications or making system changes. When you attempt to do either of these actions, UAC will pop up and interrupt you. You may either have to confirm you know what you’re doing, or even enter an administrator password if you don’t have those rights. Some users find UAC annoying and choose to disable it but this very important security feature of Windows (and we strongly caution against doing that). That’s why in this lesson, we will carefully explain what UAC is and everything it does. As you will see, this feature has an important role in keeping Windows safe from all kinds of security problems. In this lesson you will learn which activities may trigger a UAC prompt asking for permissions and how UAC can be set so that it strikes the best balance between usability and security. You will also learn what kind of information you can find in each UAC prompt. Last but not least, you will learn why you should never turn off this feature of Windows. By the time we’re done today, we think you will have a newly found appreciation for UAC, and will be able to find a happy medium between turning it off completely and letting it annoy you to distraction. What is UAC and How Does it Work? UAC or User Account Control is a security feature that helps prevent unauthorized system changes to your Windows computer or device. These changes can be made by users, applications, and sadly, malware (which is the biggest reason why UAC exists in the first place). When an important system change is initiated, Windows displays a UAC prompt asking for your permission to make the change. If you don’t give your approval, the change is not made. In Windows, you will encounter UAC prompts mostly when working with desktop applications that require administrative permissions. For example, in order to install an application, the installer (generally a setup.exe file) asks Windows for administrative permissions. UAC initiates an elevation prompt like the one shown earlier asking you whether it is okay to elevate permissions or not. If you say “Yes”, the installer starts as administrator and it is able to make the necessary system changes in order to install the application correctly. When the installer is closed, its administrator privileges are gone. If you run it again, the UAC prompt is shown again because your previous approval is not remembered. If you say “No”, the installer is not allowed to run and no system changes are made. If a system change is initiated from a user account that is not an administrator, e.g. the Guest account, the UAC prompt will also ask for the administrator password in order to give the necessary permissions. Without this password, the change won’t be made. Which Activities Trigger a UAC Prompt? There are many types of activities that may trigger a UAC prompt: Running a desktop application as an administrator Making changes to settings and files in the Windows and Program Files folders Installing or removing drivers and desktop applications Installing ActiveX controls Changing settings to Windows features like the Windows Firewall, UAC, Windows Update, Windows Defender, and others Adding, modifying, or removing user accounts Configuring Parental Controls in Windows 7 or Family Safety in Windows 8.x Running the Task Scheduler Restoring backed-up system files Viewing or changing the folders and files of another user account Changing the system date and time You will encounter UAC prompts during some or all of these activities, depending on how UAC is set on your Windows device. If this security feature is turned off, any user account or desktop application can make any of these changes without a prompt asking for permissions. In this scenario, the different forms of malware existing on the Internet will also have a higher chance of infecting and taking control of your system. In Windows 8.x operating systems you will never see a UAC prompt when working with apps from the Windows Store. That’s because these apps, by design, are not allowed to modify any system settings or files. You will encounter UAC prompts only when working with desktop programs. What You Can Learn from a UAC Prompt? When you see a UAC prompt on the screen, take time to read the information displayed so that you get a better understanding of what is going on. Each prompt first tells you the name of the program that wants to make system changes to your device, then you can see the verified publisher of that program. Dodgy software tends not to display this information and instead of a real company name, you will see an entry that says “Unknown”. If you have downloaded that program from a less than trustworthy source, then it might be better to select “No” in the UAC prompt. The prompt also shares the origin of the file that’s trying to make these changes. In most cases the file origin is “Hard drive on this computer”. You can learn more by pressing “Show details”. You will see an additional entry named “Program location” where you can see the physical location on your hard drive, for the file that’s trying to perform system changes. Make your choice based on the trust you have in the program you are trying to run and its publisher. If a less-known file from a suspicious location is requesting a UAC prompt, then you should seriously consider pressing “No”. What’s Different About Each UAC Level? Windows 7 and Windows 8.x have four UAC levels: Always notify – when this level is used, you are notified before desktop applications make changes that require administrator permissions or before you or another user account changes Windows settings like the ones mentioned earlier. When the UAC prompt is shown, the desktop is dimmed and you must choose “Yes” or “No” before you can do anything else. This is the most secure and also the most annoying way to set UAC because it triggers the most UAC prompts. Notify me only when programs/apps try to make changes to my computer (default) – Windows uses this as the default for UAC. When this level is used, you are notified before desktop applications make changes that require administrator permissions. If you are making system changes, UAC doesn’t show any prompts and it automatically gives you the necessary permissions for making the changes you desire. When a UAC prompt is shown, the desktop is dimmed and you must choose “Yes” or “No” before you can do anything else. This level is slightly less secure than the previous one because malicious programs can be created for simulating the keystrokes or mouse moves of a user and change system settings for you. If you have a good security solution in place, this scenario should never occur. Notify me only when programs/apps try to make changes to my computer (do not dim my desktop) – this level is different from the previous in in the fact that, when the UAC prompt is shown, the desktop is not dimmed. This decreases the security of your system because different kinds of desktop applications (including malware) might be able to interfere with the UAC prompt and approve changes that you might not want to be performed. Never notify – this level is the equivalent of turning off UAC. When using it, you have no protection against unauthorized system changes. Any desktop application and any user account can make system changes without your permission. How to Configure UAC If you would like to change the UAC level used by Windows, open the Control Panel, then go to “System and Security” and select “Action Center”. On the column on the left you will see an entry that says “Change User Account Control settings”. The “User Account Control Settings” window is now opened. Change the position of the UAC slider to the level you want applied then press “OK”. Depending on how UAC was initially set, you may receive a UAC prompt requiring you to confirm this change. Why You Should Never Turn Off UAC If you want to keep the security of your system at decent levels, you should never turn off UAC. When you disable it, everything and everyone can make system changes without your consent. This makes it easier for all kinds of malware to infect and take control of your system. It doesn’t matter whether you have a security suite or antivirus installed or third-party antivirus, basic common-sense measures like having UAC turned on make a big difference in keeping your devices safe from harm. We have noticed that some users disable UAC prior to setting up their Windows devices and installing third-party software on them. They keep it disabled while installing all the software they will use and enable it when done installing everything, so that they don’t have to deal with so many UAC prompts. Unfortunately this causes problems with some desktop applications. They may fail to work after you enable UAC. This happens because, when UAC is disabled, the virtualization techniques UAC uses for your applications are inactive. This means that certain user settings and files are installed in a different place and when you turn on UAC, applications stop working because they should be placed elsewhere. Therefore, whatever you do, do not turn off UAC completely! Coming up next … In the next lesson you will learn about Windows Defender, what this tool can do in Windows 7 and Windows 8.x, what’s different about it in these operating systems and how it can be used to increase the security of your system.

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• Revision control for writing programming lessons

  - by Dietrich Epp

  I'd like to write a series programming lessons that guide programmers to build a certain kind of program. After each lesson, I'd like to provide sample code that implements what that lesson covered, and the next lesson would use that code as a starting point. Right now I'm using Git to keep track of the code from lesson to lesson. Each lesson has its own branch. lesson1: A--B--C \ lesson2: D--E--F \ lesson3: G--H--I However, suppose that now I want to make it easier on the Windows programmers using my lessons, so I add a Visual Studio project to lesson 1 and then merge it into lessons 2 and 3. lesson1: A--B--C--------------J \ \ lesson2: D--E--F--------K \ \ lesson3: G--H--I--L And then someone points out a bug in lesson 2 that causes crashes on certain systems. (This diagram is where I am right now, and I'm having doubts about continuing along this path.) lesson1: A--B--C--------------J \ \ lesson2: D--E--F--------K--M \ \ \ lesson3: G--H--I--L--N Here are the problems I imagine having: If I had many lessons, and I fix something in lesson 1, am I going to have to spend fifteen minutes or more just merging that one simple change? I know I'll probably have to test all of those lessons again, but I can put that off. When I make a bunch of changes to various lessons on one computer, how do I pull all of the branches at the same time? If I decide to publish these lessons, I'd like a way to tag all of the branches to correspond with what I publish. I figure I'll just need to tag each branch separately, but it would be nice if there were a better way. When I look at the history, I imagine becoming terribly confused about what I've done. Compare the above diagram to a hypothetical diagram below, where I use rebase instead of merge (and rebase has its own problems): lesson1: A--B--C--J \ lesson2: D2--E2--F2--M \ lesson3: G2--H2--I2 Do any of you have experience working with a project like this? Should I consider using a different VCS, such as Darcs? (Note: it would be a real pain to use centralized VCS, so don't suggest one of those unless the benefits are clear.) Should I consider writing plugins or extra tools for a VCS (such as a "meta tag" which tags several branches)?

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• Access violation in DirectX OMSetRenderTargets

  - by IDWMaster

  I receive the following error (Unhandled exception at 0x527DAE81 (d3d11_1sdklayers.dll) in Lesson2.Triangles.exe: 0xC0000005: Access violation reading location 0x00000000) when running the Triangle sample application for DirectX 11 in D3D_FEATURE_LEVEL_9_1. This error occurs at the OMSetRenderTargets function, as shown below, and does not happen if I remove that function from the program (but then, the screen is blue, and does not render the triangle) //// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF //// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO //// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A //// PARTICULAR PURPOSE. //// //// Copyright (c) Microsoft Corporation. All rights reserved #include #include #include "DirectXSample.h" #include "BasicMath.h" #include "BasicReaderWriter.h" using namespace Microsoft::WRL; using namespace Windows::UI::Core; using namespace Windows::Foundation; using namespace Windows::ApplicationModel::Core; using namespace Windows::ApplicationModel::Infrastructure; // This class defines the application as a whole. ref class Direct3DTutorialViewProvider : public IViewProvider { private: CoreWindow^ m_window; ComPtr m_swapChain; ComPtr m_d3dDevice; ComPtr m_d3dDeviceContext; ComPtr m_renderTargetView; public: // This method is called on application launch. void Initialize( _In_ CoreWindow^ window, _In_ CoreApplicationView^ applicationView ) { m_window = window; } // This method is called after Initialize. void Load(_In_ Platform::String^ entryPoint) { } // This method is called after Load. void Run() { // First, create the Direct3D device. // This flag is required in order to enable compatibility with Direct2D. UINT creationFlags = D3D11_CREATE_DEVICE_BGRA_SUPPORT; #if defined(_DEBUG) // If the project is in a debug build, enable debugging via SDK Layers with this flag. creationFlags |= D3D11_CREATE_DEVICE_DEBUG; #endif // This array defines the ordering of feature levels that D3D should attempt to create. D3D_FEATURE_LEVEL featureLevels[] = { D3D_FEATURE_LEVEL_11_1, D3D_FEATURE_LEVEL_11_0, D3D_FEATURE_LEVEL_10_1, D3D_FEATURE_LEVEL_10_0, D3D_FEATURE_LEVEL_9_3, D3D_FEATURE_LEVEL_9_1 }; ComPtr d3dDevice; ComPtr d3dDeviceContext; DX::ThrowIfFailed( D3D11CreateDevice( nullptr, // specify nullptr to use the default adapter D3D_DRIVER_TYPE_HARDWARE, nullptr, // leave as nullptr if hardware is used creationFlags, // optionally set debug and Direct2D compatibility flags featureLevels, ARRAYSIZE(featureLevels), D3D11_SDK_VERSION, // always set this to D3D11_SDK_VERSION &d3dDevice, nullptr, &d3dDeviceContext ) ); // Retrieve the Direct3D 11.1 interfaces. DX::ThrowIfFailed( d3dDevice.As(&m_d3dDevice) ); DX::ThrowIfFailed( d3dDeviceContext.As(&m_d3dDeviceContext) ); // After the D3D device is created, create additional application resources. CreateWindowSizeDependentResources(); // Create a Basic Reader-Writer class to load data from disk. This class is examined // in the Resource Loading sample. BasicReaderWriter^ reader = ref new BasicReaderWriter(); // Load the raw vertex shader bytecode from disk and create a vertex shader with it. auto vertexShaderBytecode = reader-ReadData("SimpleVertexShader.cso"); ComPtr vertexShader; DX::ThrowIfFailed( m_d3dDevice-CreateVertexShader( vertexShaderBytecode-Data, vertexShaderBytecode-Length, nullptr, &vertexShader ) ); // Create an input layout that matches the layout defined in the vertex shader code. // For this lesson, this is simply a float2 vector defining the vertex position. const D3D11_INPUT_ELEMENT_DESC basicVertexLayoutDesc[] = { { "POSITION", 0, DXGI_FORMAT_R32G32_FLOAT, 0, 0, D3D11_INPUT_PER_VERTEX_DATA, 0 }, }; ComPtr inputLayout; DX::ThrowIfFailed( m_d3dDevice-CreateInputLayout( basicVertexLayoutDesc, ARRAYSIZE(basicVertexLayoutDesc), vertexShaderBytecode-Data, vertexShaderBytecode-Length, &inputLayout ) ); // Load the raw pixel shader bytecode from disk and create a pixel shader with it. auto pixelShaderBytecode = reader-ReadData("SimplePixelShader.cso"); ComPtr pixelShader; DX::ThrowIfFailed( m_d3dDevice-CreatePixelShader( pixelShaderBytecode-Data, pixelShaderBytecode-Length, nullptr, &pixelShader ) ); // Create vertex and index buffers that define a simple triangle. float3 triangleVertices[] = { float3(-0.5f, -0.5f,13.5f), float3( 0.0f, 0.5f,0), float3( 0.5f, -0.5f,0), }; D3D11_BUFFER_DESC vertexBufferDesc = {0}; vertexBufferDesc.ByteWidth = sizeof(float3) * ARRAYSIZE(triangleVertices); vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT; vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER; vertexBufferDesc.CPUAccessFlags = 0; vertexBufferDesc.MiscFlags = 0; vertexBufferDesc.StructureByteStride = 0; D3D11_SUBRESOURCE_DATA vertexBufferData; vertexBufferData.pSysMem = triangleVertices; vertexBufferData.SysMemPitch = 0; vertexBufferData.SysMemSlicePitch = 0; ComPtr vertexBuffer; DX::ThrowIfFailed( m_d3dDevice-CreateBuffer( &vertexBufferDesc, &vertexBufferData, &vertexBuffer ) ); // Once all D3D resources are created, configure the application window. // Allow the application to respond when the window size changes. m_window-SizeChanged += ref new TypedEventHandler( this, &Direct3DTutorialViewProvider::OnWindowSizeChanged ); // Specify the cursor type as the standard arrow cursor. m_window-PointerCursor = ref new CoreCursor(CoreCursorType::Arrow, 0); // Activate the application window, making it visible and enabling it to receive events. m_window-Activate(); // Enter the render loop. Note that tailored applications should never exit. while (true) { // Process events incoming to the window. m_window-Dispatcher-ProcessEvents(CoreProcessEventsOption::ProcessAllIfPresent); // Specify the render target we created as the output target. ID3D11RenderTargetView* targets[1] = {m_renderTargetView.Get()}; m_d3dDeviceContext-OMSetRenderTargets( 1, targets, NULL // use no depth stencil ); // Clear the render target to a solid color. const float clearColor[4] = { 0.071f, 0.04f, 0.561f, 1.0f }; //Code fails here m_d3dDeviceContext-ClearRenderTargetView( m_renderTargetView.Get(), clearColor ); m_d3dDeviceContext-IASetInputLayout(inputLayout.Get()); // Set the vertex and index buffers, and specify the way they define geometry. UINT stride = sizeof(float3); UINT offset = 0; m_d3dDeviceContext-IASetVertexBuffers( 0, 1, vertexBuffer.GetAddressOf(), &stride, &offset ); m_d3dDeviceContext-IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST); // Set the vertex and pixel shader stage state. m_d3dDeviceContext-VSSetShader( vertexShader.Get(), nullptr, 0 ); m_d3dDeviceContext-PSSetShader( pixelShader.Get(), nullptr, 0 ); // Draw the cube. m_d3dDeviceContext-Draw(3,0); // Present the rendered image to the window. Because the maximum frame latency is set to 1, // the render loop will generally be throttled to the screen refresh rate, typically around // 60Hz, by sleeping the application on Present until the screen is refreshed. DX::ThrowIfFailed( m_swapChain-Present(1, 0) ); } } // This method is called before the application exits. void Uninitialize() { } private: // This method is called whenever the application window size changes. void OnWindowSizeChanged( _In_ CoreWindow^ sender, _In_ WindowSizeChangedEventArgs^ args ) { m_renderTargetView = nullptr; CreateWindowSizeDependentResources(); } // This method creates all application resources that depend on // the application window size. It is called at app initialization, // and whenever the application window size changes. void CreateWindowSizeDependentResources() { if (m_swapChain != nullptr) { // If the swap chain already exists, resize it. DX::ThrowIfFailed( m_swapChain-ResizeBuffers( 2, 0, 0, DXGI_FORMAT_R8G8B8A8_UNORM, 0 ) ); } else { // If the swap chain does not exist, create it. DXGI_SWAP_CHAIN_DESC1 swapChainDesc = {0}; swapChainDesc.Stereo = false; swapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT; swapChainDesc.Scaling = DXGI_SCALING_NONE; swapChainDesc.Flags = 0; // Use automatic sizing. swapChainDesc.Width = 0; swapChainDesc.Height = 0; // This is the most common swap chain format. swapChainDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM; // Don't use multi-sampling. swapChainDesc.SampleDesc.Count = 1; swapChainDesc.SampleDesc.Quality = 0; // Use two buffers to enable flip effect. swapChainDesc.BufferCount = 2; // We recommend using this swap effect for all applications. swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL; // Once the swap chain description is configured, it must be // created on the same adapter as the existing D3D Device. // First, retrieve the underlying DXGI Device from the D3D Device. ComPtr dxgiDevice; DX::ThrowIfFailed( m_d3dDevice.As(&dxgiDevice) ); // Ensure that DXGI does not queue more than one frame at a time. This both reduces // latency and ensures that the application will only render after each VSync, minimizing // power consumption. DX::ThrowIfFailed( dxgiDevice-SetMaximumFrameLatency(1) ); // Next, get the parent factory from the DXGI Device. ComPtr dxgiAdapter; DX::ThrowIfFailed( dxgiDevice-GetAdapter(&dxgiAdapter) ); ComPtr dxgiFactory; DX::ThrowIfFailed( dxgiAdapter-GetParent( __uuidof(IDXGIFactory2), &dxgiFactory ) ); // Finally, create the swap chain. DX::ThrowIfFailed( dxgiFactory-CreateSwapChainForImmersiveWindow( m_d3dDevice.Get(), DX::GetIUnknown(m_window), &swapChainDesc, nullptr, // allow on all displays &m_swapChain ) ); } // Once the swap chain is created, create a render target view. This will // allow Direct3D to render graphics to the window. ComPtr backBuffer; DX::ThrowIfFailed( m_swapChain-GetBuffer( 0, __uuidof(ID3D11Texture2D), &backBuffer ) ); DX::ThrowIfFailed( m_d3dDevice-CreateRenderTargetView( backBuffer.Get(), nullptr, &m_renderTargetView ) ); // After the render target view is created, specify that the viewport, // which describes what portion of the window to draw to, should cover // the entire window. D3D11_TEXTURE2D_DESC backBufferDesc = {0}; backBuffer-GetDesc(&backBufferDesc); D3D11_VIEWPORT viewport; viewport.TopLeftX = 0.0f; viewport.TopLeftY = 0.0f; viewport.Width = static_cast(backBufferDesc.Width); viewport.Height = static_cast(backBufferDesc.Height); viewport.MinDepth = D3D11_MIN_DEPTH; viewport.MaxDepth = D3D11_MAX_DEPTH; m_d3dDeviceContext-RSSetViewports(1, &viewport); } }; // This class defines how to create the custom View Provider defined above. ref class Direct3DTutorialViewProviderFactory : IViewProviderFactory { public: IViewProvider^ CreateViewProvider() { return ref new Direct3DTutorialViewProvider(); } }; [Platform::MTAThread] int main(array^) { auto viewProviderFactory = ref new Direct3DTutorialViewProviderFactory(); Windows::ApplicationModel::Core::CoreApplication::Run(viewProviderFactory); return 0; }

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