ARTICLES IN THE BOOK
A GUIDE TO WINDOWS VISTA
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There are a number of security and safety features new to Windows Vista, most of which are not available in any prior Microsoft Windows operating system release.
Beginning in early 2002 with Microsoft's announcement of their Trustworthy Computing initiative, a great deal of work has gone into making Windows Vista a more secure operating system than its predecessors. Internally, Microsoft adopted a "Security Development Lifecycle" with the underlying ethos of, "Secure by design, secure by default, secure in deployment". New code for Windows Vista was developed with the SDL methodology, and all existing code was reviewed and refactored to improve security.
Some specific areas where Windows Vista introduces new security and safety mechanisms include User Account Control, parental controls, Network Access Protection, a built-in anti-malware tool, and new digital content protection mechanisms.
But new vulnerabilities have already been found, some of which are still not fixed, according to security websites Secunia and SecurityFocus.
User Account Control is a new infrastructure that requires user consent before allowing any action that requires administrative privileges. With this feature, all users, including users with administrative privileges, run in a standard user mode by default, since most applications do not require higher privileges. When some action is attempted that needs administrative privileges, such as installing new software or changing system settings, Windows will prompt the user whether to allow the action or not. If the user chooses to allow, the process initiating the action is elevated to a higher privilege context to continue. While standard users need to enter a username and password of an administrative account to get a process elevated (Over-the-shoulder Credentials), an administrator can choose to be prompted just for consent or ask for credentials.
UAC asks for credentials in a Secure Desktop mode, where the entire screen is faded out and temporarily disabled, to present only the elevation UI. This is to prevent spoofing of the UI or the mouse by the application requesting elevation. Any application requesting elevation has to have focus before the switch to Secure Desktop occurs. Else its taskbar icon blinks, and when focussed, the elevation UI is presented. Since the Secure Desktop allows only highest privilege System applications to run, no user mode application can present its dialog boxes, so any prompt for elevation consent can be safely assumed to be genuine. Additionally, they can also help protect against shatter attacks, which intercept Windows inter-process messages to run malicious code or spoof the user interface, by preventing unauthorized processes from sending messages to high privilege processes. Any process that wants to send a message to a high privilege process must get itself elevated to the higher privilege context, via UAC.
Many applications break for standard users (non-admins) today because they attempt to write to protected areas that the standard user does not have access to. UAC will improve application compatibility for these users by redirecting writes (and subsequent reads) to a per-user location within the user’s profile. For example, if an application attempts to write to “C:\program files\appname\settings.ini” and the user doesn’t have permissions to write to that directory, the write will get redirected to “C:\Users\username\AppData\Local\VirtualStore\Program Files\appname\.” To make it easier to find these redirected files has been added a new button to Windows Explorer. If there is a virtualized version of a file related to the current directory, a Compatibility Files button appears that will take you to the virtual location to view that file.
Windows Vista includes Windows Defender, Microsoft's anti-spyware utility. According to Microsoft, it was renamed from 'Microsoft AntiSpyware' because it not only features scanning of the system for spyware, similar to other free products on the market, but also includes Real Time Security agents that monitor several common areas of Windows for changes which may be caused by spyware. These areas include Internet Explorer configuration and downloads, auto-start applications, system configuration settings, and add-ons to Windows such as Windows Shell extensions.
Windows Defender also includes the ability to easily remove ActiveX applications that are installed. It also incorporates the SpyNet network, which allows users to communicate with Microsoft, send what they consider is spyware, and check what applications are acceptable.
Windows Vista includes a range of parental controls. An administrator can apply parental control restrictions to other users on the computer. Facilities include:
Windows Vista uses Address Space Layout Randomization (ASLR) to load system files at random addresses in memory. By default, all system files are loaded randomly at any of the possible 256 locations. Other executables have to specifically set a bit in the header of the PE file, which is the file format for Windows executables to use ASLR. For such executables, the stack and heap allocated is randomly decided. By loading system files at random addresses, it becomes harder for malicious code to know where privileged system functions are located, thereby making it unlikely for them to predictably use them. This helps prevent most remote execution attacks by preventing Return-to-libc attacks.
The Portable Executable format has been updated to support embedding of exception handler address in the header. Whenever an exception is thrown, the address of the handler is verified with the one stored in the executable header. If they match, the exception is handled, otherwise it indicates that the run-time stack has been compromised, and hence the process is terminated.
Function pointers are obfuscated by XOR-ing with a random number, so that the actual address pointed to is hard to retrieve. So would be to manually change a pointer, as the obfuscation key used for the pointer would be very hard to retrieve. Thus, it is made hard for any unauthorized user of the function pointer to be able to actually use it. Also metadata for heap blocks are XOR-ed with random numbers. In addition, check-sums for heap blocks are maintained, which is used to detect unauthorized changes and heap corruption. Whenever a heap corruption is detected, the application is killed to prevent successful completion of the exploit.
Windows Vista binaries include intrinsic support for detection of stack-overflow. When a stack overflow in Windows Vista binaries is detected, the process is killed so that it cannot be used to carry on the exploit. Also Windows Vista binaries place buffers higher in memory and non buffers, like pointers and supplied parameters, in lower memory area. So to actually exploit, a buffer underrun is needed to gain access to those locations. However, buffer underruns are much less common than buffer overruns.
Windows Vista also uses processor-enforced Data Execution Prevention on all processes to mark some memory pages as non-executable data segments (like the heap and stack), and subsequently any data is prevented from being interpreted and executed as code. This prevents exploit code from being injected as data and then executed. Though DEP was present in Windows XP Service Pack 2 and Windows Server 2003 Service Pack 1, its enforcement has been made stricter[verification needed] in Windows Vista.
DEP is still not enforced for all applications by default in Vista and is only turned on for critical system components. When a user turns on DEP for all applications they can gain additional resistance against zero-day exploits. Some applications will generate DEP exceptions and Windows XP SP2 would give you an easy way to create an application exception during runtime if an application violates DEP but it's possible that this could be social engineered. Vista seems to lack this ability to make on-the-fly exceptions to DEP and a user would have to manually create one.
Microsoft is introducing a number of Digital Rights Management and content-protection features in Windows Vista, to help digital content providers, corporations, and end-users protect their data from being copied.
These features have been criticised by some as more restrictive than useful for the user.
Windows Vista introduces Mandatory Integrity Control to set integrity levels for processes. A low integrity process can not access the resources of a higher integrity process. This feature is being used to enforce application isolation, where applications in a medium integrity level, such as all applications running in the standard user context can not hook into system level processes which run in high integrity level, such as administrator mode applications but can hook onto lower integrity processes like Windows Internet Explorer 7. A lower privilege process cannot perform a window handle validation of higher process privilege, cannot SendMessage or PostMessage to higher privilege application windows, cannot use thread hooks to attach to a higher privilege process, cannot use Journal hooks to monitor a higher privilege process and cannot perform DLL–injection to a higher privilege process.
A new security feature called Windows Service Hardening prevents Windows services from doing operations on file systems, registry or networks which they are not supposed to, thereby preventing entry of malware by piggybacking on system services. Services are now assigned a per-service Security identifier (SID), which allows controlling access to the service as per the access specified by the security identifier. Services can also use access control lists (ACL) to prevent external access to resources private to itself. Services in Windows Vista also run in a less privileged account such as Local Service or Network Service, instead of the System account. Services will also need explicit write permissions to write to resources, on a per-service basis. Only those resources which have to be modified by a service give it write access. So trying to modify any other resource fails. Services will also have pre-configured firewall policy, which gives it only as much privilege as is needed for it to function properly. Independent software vendors can also use Windows Service Hardening to harden their own services.
Network Access Protection (NAP), which makes sure that computers connecting to a network or communicating over a network conform to a required level of system health as has been set by the administrator of the network, has been upgraded significantly in Windows Vista. Depending on the policy set by the administrator, the computers which do not meet the requirements will either be warned and granted access or allowed a limited access to network resources or completely denied access. NAP can also optionally provide software updates to a non-compliant computer to upgrade itself to the level as required to access the network, using a Remediation Server. A conforming client is given a Health Certificate, which it then uses to access protected resources on the network.
A Network Policy Server, running Windows Server "Longhorn" acts as health policy server and clients need to use Windows Vista or better. A VPN server, RADIUS server or DHCP server can also act as the health policy server.
Graphical identification and authentication (GINA), used for secure authentication and interactive logon has been replaced by Credential Providers. Combined with supporting hardware, Credential Providers can extend the operating system to enable users to logon through biometric devices (fingerprint, retinal, or voice recognition), passwords, PINs and smart card certificates, or any custom authentication package and schema third party developers wish to create. Enterprises may develop, deploy, and optionally enforce custom authentication mechanisms for all domain users. Credential Providers may be designed to support Single sign-on (SSO), authenticating users to a secure network access point (leveraging RADIUS and other technologies) as well as machine logon. Credential Providers are also designed to support application-specific credential gathering, and may be used for authentication to network resources, joining machines to a domain, or to provide administrator consent for User Account Control. Fast User Switching which was limited to workgroup computers on Windows XP, can now also be enabled for computers joined to a domain, starting with Windows Vista.
Crypto NexGen (CNG), is an update to the Crypto API, featuring support for plugging in custom cryptographic APIs into the CNG runtime. Also, CNG will support Elliptic Curve Cryptography. The CNG API will also integrate with the smart-card subsystem by including a Base Smart Card Cryptographic Service Provider (Base CSP) module which encapsulates the smart card API. Smart card manufacturers just have to make their devices compatible with this, rather than provide a from-scratch solution.
A number of specific changes have been made:
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